The 22-year-old is so highly regarded that he is ranked as MLB.com's No. 1 left-handed pitching prospect in the Majors.
The Marlins have not had a dominating left-handed starter since Dontrelle Willis burst onto the big league scene as a 21-year-old in 2003. Since then, they've had some quality lefty starters. Scott Olsen won 12 games as a rookie in 2006, but his career fizzled fast.
More recently, Mark Buehrle was signed as an established free agent in 2012, and he went 13-13 in his lone season in Miami. The former All-Star was abruptly traded to Toronto as part of a blockbuster 12-player deal.
Now, the path is clear for Heaney to become the best lefty prospect in Miami since the D-Train was rolling along to the NL Rookie of the Year Award in '03 and setting a franchise record with 22 wins in '05.
But Heaney isn't the only lefty prospect garnering preseason praise. He has company in the Minor League system. Justin Nicolino, acquired from Toronto as part of the Buehrle deal, also has cracked MLB.com's Top 10, rated the seventh-best lefty prospect.
The Marlins are excited about their overall pitching depth, which is filled with quality arms from the big leagues on down.
Heaney and Nicolino are in the process of rising up the ranks. Both will get long looks in Spring Training, but neither will be rushed to the big leagues. Chances are Heaney and Nicolino will play for the Marlins in 2014, it just may not be by Opening Day.
Some may say, "Why not?"
Fair point, especially since Miami has not been bashful about nudging young players into the big leagues. Willis made the leap after just six Double-A starts in '03. Olsen, Josh Johnson and Anibal Sanchez were 22 when they got the MLB call.
A year ago, the organization was even bolder. When Nathan Eovaldi and Henderson Alvarez went on the disabled list the day before the season opened, Fernandez was promoted at age 20 while not having pitched higher than Class A ball.
Heaney made a name for himself at Oklahoma State University, and he was the No. 9 overall pick in the 2012 First-Year Player Draft. In '13, his first full season in professional baseball, the left-hander posted eye-raising numbers at Class A Advanced Jupiter as well as Double-A Jacksonville, posting a combined 9-3 record with a 1.60 ERA. In 95 1/3 innings, Heaney struck out 89, walked 26 and had a WHIP of 1.07.
Durability was a concern, as Heaney missed time early in the year with a strained lat muscle. For extra work and experience, he was sent to the Arizona Fall League, and he continued to impress. In 27 2/3 innings, Heaney posted a 1.95 ERA. His showing cemented him as the No. 1 lefty prospect.
Nicolino, meanwhile, enjoyed a standout 2013 season. Like Heaney, he saw action at Jupiter and Jacksonville. In 27 starts, Nicolino combined for an 8-4 record with a 3.11 ERA, logging 142 total innings.
If Nicolino doesn't make the Opening Day rotation, he could find himself starting off at Triple-A New Orleans, or back at Jacksonville, where he made nine starts.
When it comes to promoting prospects to the big leagues, numerous factors come into play. The team has to ask itself if a player is physically and mentally ready. There is tremendous wear and tear placed on starting pitchers, and both Heaney and Nicolino are slender in frame.
Also, you can't discount service time and the business side of the game. With such a premium placed on pitching, all teams are mindful of when to start the service-time clock, especially on a young arm.
Fernandez was the exception in '13. In fairness, no one is expecting Heaney to match the historic rookie season Fernandez enjoyed in 2013. Still, Heaney is capable of offering a left-handed complement to the All-Star right-hander.
Overall pitching depth also is working against Heaney and Nicolino being in the rotation in early April. The Marlins have strong starting candidates with MLB experience. Fernandez, Eovaldi, Alvarez, Jacob Turner and Tom Koehler all are big league tested, which decreases the urgency to speed along the development of Heaney and Nicolino.