The Marlins also have invited 16 of their organizational players, including Colin Moran, the sixth overall pick in the 2013 First-Year Player Draft, and Andrew Heaney, a standout left-hander who is regarded as a future top-of-the-rotation prospect.
Slowey, a non-roster invitee with Miami last year, made the team. He went 3-6 with a 4.11 ERA in 92 innings over 20 appearances (14 starts) before he was sidelined in late July with right forearm discomfort.
Benson will be interesting to watch. The 25-year-old is a right-handed hitter with power potential. He last appeared in the big leagues in 2011 with Minnesota, when he appeared in 21 games. Benson was in the Twins and Rangers systems last year.
In recent years, the Marlins have had success with non-roster invitees. A year ago, Slowey and reliever Chad Qualls capitalized on their opportunities and each contributed to the club.
The Marlins were looking to add a lefty reliever candidate, and Spence will get a look. A native of Australia, Spence has 51 games of MLB experience when he was with the Padres in 2011-12.
At this point, Miami has 62 players set to report to Spring Training, which begins with pitchers and catchers workouts on Feb. 16 at the Roger Dean Stadium complex in Jupiter, Fla. Position players report on Feb. 20.
Moran, a left-handed-hitting third baseman, is likely to open the year at either Advanced Class A Jupiter or Double-A Jacksonville. At Class A Greensboro last year, he batted .299 with four homers and 23 RBIs in 42 games.
The other 14 receiving invitations are right-handed pitchers Anthony DeSclafani, Bryan Evans, Colby Suggs, Rett Varner and Nick Wittgren; left-handed pitchers Adam Conley, James Leverton, Greg Nappo and Justin Nicolino; catchers Austin Barnes and Kyle Skipworth; and infielders Danny Black, Mark Canha, Moran and Austin Nola.
At Jupiter and Jacksonville last year, Heaney combined for a 9-3 record with a 1.60 ERA in 95 1/3 total innings. A year ago, he was in Spring Training with the Marlins, but he was hindered by a lat injury. Heaney also was a standout in the Arizona Fall League, where he was posted a 1.95 ERA in 27 2/3 innings.
Miami has some high-end pitching prospects. In Spring Training, the club will get a look at a number of candidates who promise to be part of its future.
Nicolino and Conley are a pair of lefties who are getting closer to being big league-ready. So is DeSclafani, named the organizational pitcher of the year in 2013.
Wittgren, a right-handed reliever, was dominant in the Arizona Fall League, striking out 19 in 13 2/3 innings.