Players are graded on a 20-80 scale for future tools -- 20-30 is well below average, 40 is below average, 50 is average, 60 is above average and 70-80 is well above average.
Check out all 30 team Top 20 lists and the Top 100 on Prospect Watch.
1. Andrew Heaney, LHP
Preseason rank: 1
MLB Top 100 rank: 22 (Preseason: 29)
Scouting grades: Fastball: 60 | Slider: 65 | Changeup: 55 | Control: 60 | Overall: 60
Drafted as a potentially quick-to-the-big-leagues college lefty, Heaney has been just that, reaching Miami's rotation in just his second full professional season, after being slowed slightly by injury during his first year in the Marlins' system.
Heaney's fastball sits in the low 90s, and it reaches 95 mph regularly. He mixes it with a wipeout slider and a changeup that has developed into a good third pitch. The improvement of Heaney's changeup has given him a weapon to combat right-handed hitters, and he actually performed better against them than he did against left-handed hitters in 2013.
Heaney already had advanced pitchability coming out of Oklahoma State, and that has only gotten better, as he has worked to improve his tempo and his control of the running game. That helped him climb from Double-A to Triple-A in 2014, and he eventually made his Major League debut on June 19, just two years after being drafted.
2. Tyler Kolek, RHP
Preseason rank: None (2014 Draft)
MLB Top 100 rank: 27 (Preseason: NA)
Scouting grades: Fastball: 80 | Slider: 65 | Curveball: 60 | Changeup: 45 | Control: 45 | Overall: 60
Ranked No. 3 on MLB.com's Top 200 Draft Prospects, Kolek's combination of size and stuff made him a legitimate candidate to become the first high school right-hander to go No. 1 overall. Instead, it was the Marlins who nabbed him with the second selection, and they gave him $6 million to sign.
Kolek had the best fastball in the 2014 First-Year Player Draft class, consistently topping 100 mph during his senior year of high school in Texas. He throws a pair of breaking balls, a 12-to-6 curve and a sharp slider, with the latter having more upside, even though he started throwing it more recently. Kolek hasn't needed a changeup, but he's shown some feel for it, and it could be an average pitch in the future.
For Kolek to reach his potential as a top-of-the-rotation starter, he will have to refine his control and command. If it catches up to his electric stuff, Major League hitters could be in serious trouble.
3. Colin Moran, 3B
Preseason rank: 2
MLB Top 100 rank: 72 (Preseason: 51)
Scouting grades: Hit: 65 | Power: 50 | Run: 40 | Arm: 55 | Field: 50 | Overall: 55
Seen as a safe pick, Moran garnered some consideration for the first overall pick of the 2013 Draft before landing with the Marlins at No. 6 overall. He comes from a baseball family (his uncle, B.J. Surhoff, and his brother, Brian Moran, have both played professionally), and he has a good understanding of the game.
Moran is a pure hitter with an advanced approach. Scouts wonder how much power he will have, however, as his swing is more geared to produce line drives than home runs. Moran is a below-average runner, but it doesn't hold him back defensively. He is sure-handed, and he has a strong arm.
While Moran's power will likely determine his impact, few doubt he will become a solid Major Leaguer.
4. Anthony DeSclafani, RHP
Preseason rank: 6
Scouting grades: Fastball: 60 | Slider: 55 | Changeup: 45 | Control: 55 | Overall: 50
Mostly a reliever at the University of Florida, DeSclafani began his professional career with the Toronto Blue Jays, pitching mostly as a starter. That continued in the right-hander's first season with Miami, as he joined the organization in the big trade between the teams in November 2012, carrying him to the big league rotation in '14.
DeSclafani shows three workable pitches, giving him the chance to remain a starter. Aggressive on the mound, he pitches off of his above-average fastball, and while he's used two breaking balls in the past, he is now focused on his slider, which looks like a future out pitch.
DeSclafani tends to be too firm with his changeup, but if he can take a little more off of it to separate it from his fastball, he could stick in the Marlins' rotation for a long time.
5. Justin Nicolino, LHP
Preseason rank: 4
Scouting grades: Fastball: 55 | Curveball: 50 | Changeup: 60 | Control: 60 | Overall: 50
Nicolino was a part of the package Miami received in its blockbuster trade with Toronto in November 2012. A polished left-hander, he has a good feel for pitching and a chance to have three pitches that are at least Major League average.
Nicolino throws his fastball in the low 90s, with good tailing movement. His best pitch is his changeup, and he also throws a big sweeping curveball. All of Nicolino's pitches play up due to his above-average command. He earns praise for his intelligence and poise on the mound.
The Blue Jays were cautious with Nicolino's development, but the Marlins gave him a little more leash, and he reached Double-A Jacksonville in 2013. If he continues to move more quickly, he could be in Miami before too long.
6. Avery Romero, 2B
Preseason rank: 11
Scouting grades: Hit: 55 | Power: 45 | Run: 40 | Arm: 60 | Field: 50 | Overall: 50
A high school shortstop who received an above-pick-value deal to sign in 2012, Romero has moved to the right side of the diamond, and he has the makings of an offensive-minded second baseman.
Romero made strides with his defense at second, improving his footwork around the bag considerably. His best defensive tool is his arm, and he could someday get a look at third as a result, though he'll continue as an everyday second baseman for the time being.
It's Romero's bat that will carry him up the ladder. He's an aggressive hitter, one whose lack of patience can hurt at times. But Romero is a good fastball hitter, doing more damage to the pull side, with strong hands, a quick bat and more power to come as he matures.
7. Trevor Williams, RHP
Preseason rank: 10
Scouting grades: Fastball: 55 | Slider: 50 | Changeup: 50 | Control: 60 | Overall: 50
Scouts have always liked Williams' combination of solid stuff and command, even if his results at Arizona State were mixed, and the Marlins were definitely enthused with his pro mindset when he joined the organization.
Williams has always had a good arm, and Miami has helped him clean up his delivery so that he can pitch downhill more. That should help him use his three-pitch mix more effectively. Williams will throw a two-seam and a four-seam fastball, complementing those with a Major League-average slider and changeup.
With his polish and firm sense of a game plan, Williams has shown the ability to handle an aggressive assignment, and the Marlins hope he will be the kind of college arm that doesn't take too long to get to the big leagues.
8. J.T. Realmuto, C
Preseason rank: 9
Scouting grades: Hit: 50 | Power: 40 | Run: 35 | Arm: 55 | Field: 55 | Overall: 50
Realmuto didn't begin to catch until he reached pro ball in 2010, but he's developed into a solid receiver in a short amount of time.
Realmuto's athleticism shows behind the plate, showing good range to go along with excellent hands and an above-average arm. The nuances of the craft, like calling games and blocking balls, continue to come to him.
While Realmuto's offensive game hasn't taken the same steps forward, he is at his best when he remembers to use the right side of the field and go back up the middle. If he can get back to that approach, he has the chance to be an everyday backstop, though his glove work alone should lead to a career as a backup, at the very least.
9. Adam Conley, LHP
Preseason rank: 5
Scouting grades: Fastball: 65 | Slider: 50 | Changeup: 60 | Control: 50 | Overall: 50
One of the areas of depth in Miami's system is its crop of interesting left-handed pitching. While Conley doesn't top the list, he certainly has the potential to impact the big league staff, and in the not-too-distant future.
Many thought Conley might be destined for the bullpen one day, and while the Marlins haven't discounted the possibility entirely, they still are hoping the southpaw will develop as a rotation candidate.
The key to that will be Conley's breaking ball, to go along with his above-average fastball and solid changeup. His slider has improved, though it's not a finished project yet. Conley knows he has to establish it as a consistently Major League-average offering to be a starter long term.
10. Jose Urena, RHP
Preseason rank: 8
Scouting grades: Fastball: 65 | Slider: 45 | Changeup: 50 | Control: 55 | Overall: 45
It remains to be seen what role Urena will have when he reaches the big leagues, but his combination of arm strength and makeup have people confident he'll get there.
The Dominican right-hander has an above-average fastball that can touch the mid 90s, and he combines it with a solid changeup that has improved considerably. Urena's breaking ball is a combination of a slider and a curve, and it needs to be refined for it to become a consistent weapon in his arsenal.
If that happens, Urena has the chance to start, especially with his above-average command. If it doesn't, he has the chance to be a very good two-pitch bullpen option in the future.
11. Brian Flynn, LHP
Preseason rank: 7
Scouting grades: Fastball: 60 | Slider: 55 | Curveball: 40 | Changeup: 50 | Control: 50 | Overall: 45
Fans wondering what to make of Flynn shouldn't base their opinions solely on his brief uneven stint in the big leagues. The lefty, who arrived via a 2012 Deadline deal with the Tigers, has the makings of a solid starting pitcher.
When he's going right, Flynn mixes four pitches. He commands his fastball, especially in the bottom of the zone. Flynn's curve is more of a "get-it-over" pitch early in counts, but he can work his slightly-above-average slider and average changeup off of his fastball effectively.
After Flynn pitched at three levels in 2013, the Marlins are confident his struggles in Miami last year were based more on fatigue than anything, and they are excited to see how he can contribute.
12. Domingo German, RHP
Preseason rank: None
Scouting grades: Fastball: 60 | Slider: 40 | Changeup: 50 | Control: 50 | Overall: 45
Since signing out of the Dominican Republic in 2009, German has made slow and steady progress at the lower levels of Miami's system. He might now be poised to take off.
German stands out because of his combination of upside and ceiling with feel for pitching. He has a three-pitch mix. German's fastball is a power sinker that sits in the 91-94 mph zone. His best secondary offering is his above-average changeup, and he has an advanced feel for the offspeed pitch already. German's slider is a work in progress, thrown at 81-84 mph, but it's still a little too slurvy at the moment. He's generally been a strike-thrower throughout his brief Minor League career.
German might be a step or two behind the arms that have been generating buzz at the upper levels of the Minors and in the big leagues, but he should be snapping at their heels soon.
13. Jarlin Garcia, LHP
Preseason rank: None
Scouting grades: Fastball: 60 | Curveball: 50 | Changeup: 40 | Control: 50| Overall: 45
That's right -- another left-handed-pitching prospect worth tracking in the Marlins' system.
Garcia, signed out of the Dominican Republic back in August 2010, made his full-season debut in '14 after a very strong turn in the New York-Penn League a year prior. He has an interesting three-pitch mix, with his low-90s fastball, a very good breaking ball and a developing changeup. Garcia's control is ahead of his command, but he doesn't hurt himself with walks, and he gets high marks for his maturity.
Garcia has some room for growth and a clean delivery, giving hope that there's some upside to reach for this southpaw as a future member of a big league rotation.
14. Sam Dyson, RHP
Preseason rank: 14
Scouting grades: Fastball: 60 | Slider: 45 | Changeup: 50 | Control: 50 | Overall: 45
Another young Marlins arm with experience in a variety of pitching roles, Dyson started in the Minors during his first season with the organization, but he saw time out of the bullpen when he got to Miami.
Dyson pitches off of his heavy fastball, one that can touch the mid 90s at times and generates a ton of ground balls. His best secondary pitch is a solid changeup. Dyson began 2013 throwing a curve, but he started focusing on a slider, and he seemed to respond to that better. A more consistent third pitch would be needed for him to be a starter in the big leagues.
Dyson has pitched exclusively out of the bullpen in 2014, and he reached Miami again in that role, making it seem much more likely that relief will be his long-term gig.
15. Justin Twine, SS
Preseason rank: None (2014 Draft)
Scouting grades: Hit: 45 | Power: 45 | Run: 65 | Arm: 50 | Field: 45 | Overall: 45
A football star and track standout in high school, the Marlins clearly liked Twine's athleticsm enough to nab him in the second round and give him full pick value at slightly more than $1.3 million to sign.
Twine, who did draw some interest from college football programs as a gifted running quarterback, does have well-above-average speed, especially once he's underway. The switch-hitter has a bit of a long swing, which hurts him offensively and slows him a bit getting out of the box. The Texas high school athlete isn't all raw, with some bat speed and strength to give hope of offensive upside, especially as he improves his approach at the plate. It's unclear whether Twine has the defensive chops for shortstop, but he might have the tools to make a solid center fielder.
Twine might be a bit of a project, one whom Miami will have to be patient with, but the payoff could be tremendous.
16. Colby Suggs, RHP
Preseason rank: 12
Scouting grades: Fastball: 70 | Curveball: 55 | Changeup: 40 | Control: 45 | Overall: 45
Off the mound, Suggs is polite and professional. On it, the former Arkansas closer is quite the opposite.
The bulldog right-hander is all power on the mound, with a nasty fastball-curveball combination. Suggs likes to throw his four-seamer up in the zone, and he combies it with a 12-to-6 curve that has a short late break. He began working on a changeup to give himself a third pitch against left-handed hitters, but he'll likely make a living off the first two offerings.
Suggs has struggled with his command at times, but when he repeats his delivery and throws strikes, his above-average stuff is tough to hit. He has all the makings of a late-inning bullpen guy in the near future.
17. Austin Dean, OF
Preseason rank: 20
Scouting grades: Hit: 45 | Power:45 | Run: 50 | Arm: 50 | Field: 50 | Overall: 45
A shortstop in the Texas high school ranks, Dean has played nothing but the outfield as a professional, and he has the upside to be a pretty good corner guy in the future.
Dean has a quick bat, with some power that has yet to show up in games. He needs to continue to improve his arm strength to show he can be more than a left fielder, though he'll see plenty of time in right field in 2014. And there's always the chance Dean could get another look at the infield in the future. He gets high marks for his work ethic and passion for the game.
Regardless of where Dean plays defensively, he gives the Marlins the potential to have something they don't have a lot of in their system: a right-handed corner bat with some pop.
18. Austin Barnes, 2B/C
Preseason rank: 17
Scouting grades: Hit: 50 | Power: 30 | Run: 40 | Arm: 50 | Field: 50 | Overall: 45
While Barnes' tools don't necessarily jump off the page, he's the kind of prospect whose whole is greater than the sum of his parts.
Initially a second baseman entering pro ball, Miami moved Barnes behind the plate in 2013, and he showed some solid tools there. He'll continue to get time behind the plate, but he should also see time back at second, as well as at third, to see what he can do as he expands his versatility. A solid-average hitter, Barnes uses the whole field, really understands situational hitting and is an above-average baserunner. His instincts and his makeup allow him to play above his tools.
Barnes could end up being a super-utility guy, and he's still young enough to settle into one position to be a regular at one spot. Either way, he's going to be the kind of player big league managers will want to have on their roster.
19. Austin Brice, RHP
Preseason rank: 19
Scouting grades: Fastball: 60 | Curveball: 45 | Changeup: 40 | Control: 40 | Overall: 45
Brice has the size and the arm strength. It's just a matter of the young right-hander using them consistently on the mound.
Brice still has a very high ceiling, but he has a ways to go. After moving to the 'pen for a while in 2013, he was moved back to the rotation in '14, where the hope is that he can start finding the strike zone more consistently. When Brice is throwing well, he has an above-average fastball, and his curve will show glimpses of being better than average, as well. His changeup is clearly his third pitch.
More than anything, though, it's the lack of strikes that has gotten in Brice's way. If he can figure it out and find some consistency, he has the pure stuff to fit in the middle of a big league rotation.
20. Nick Wittgren, RHP
Preseason rank: 13
Scouting grades: Fastball: 60 | Curveball: 55 | Changeup: 40 | Control: 60| Overall: 45
Wittgren's pure stuff may not jump off the page, but he's been very effective, and it's hard to argue when you look at the video game numbers he's put up so far.
Wittgren's competitiveness on the mound plays well at the back end of a bullpen. His high front-side delivery adds deception, allowing his 91-94 mph heater to play up. Wittgren couples his fastball with an above-average curve, and he can throw both for strikes at any point in the count. He's been working to develop a changeup, but it's cleary his third pitch.
In a short-relief role, that may not matter too much. Even if Wittgren's pure stuff doesn't fit the prototype for a closer, no one in Miami is betting against his ability to fill the role, should the opportunity arise.