Marcos Mateo

With a late-June call-up to San Diego, Mateo officially cemented his status as a Tommy John success story, reaching the majors again after a three-year absence. The results were far better in 2015 than those from his time with the Cubs from 2010-11, as Mateo was able to limit the free passes while also missing bats at a high clip (29.2 percent) en route to a 4.00 ERA and 1.15 WHIP in 26 appearances. The long ball haunted him a bit -- Mateo gave up five home runs in 27 frames -- but he finished strong, with just two earned runs (one homer) allowed in his final 11 appearances. Mateo should be able to solidify his spot in the bullpen in spring training and the back-end roles are relatively wide open, but he will face competition from the likes of Jon Edwards, Brandon Maurer, Nick Vincent and Kevin Quackenbush for high-leverage work.