Trevor Rosenthal, RHP, St. Louis Cardinals - Coming off a season in which he out-pitched his 4.11 ERA (120.1 innings, 111 hits, seven home runs, 133:39 K:BB, 3.07 FIP) as a 21-year-old in the Midwest League (Low-A) in 2011, Rosenthal skipped the Florida State League and started 2012 in the Double-A Texas League. In 17 starts there and three more in the Pacific Coast League, he proved to be the solid mid-rotation starter many expected (109 innings, 78 hits, 36 earned runs, seven home runs, 104:42 K:BB). As a starter, Rosenthal would attack hitters with a fastball in the low-90s, which at times touched 96 mph, along with his curveball and changeup. Both secondary offerings are average major league pitches, though he is throwing two variations of his curveball these days. It was not until Rosenthal was moved to the bullpen upon being called up to the majors that his stuff started to really play up. Out of the bullpen, his average fastball was at 97 mph and he was routinely touching 100. His regular season numbers (22.2 innings, 14 hits, seven earned runs, two home runs, 25:7 K:BB) alone would have been enough for him to make this list, but he was absolutely untouchable in the playoffs as well (8.2 innings, two hits, no runs, 15:2 K:BB).
It's unclear what Rosenthal's role in 2013 will be at this point (given the choice, I would let him continue his dominance out of the bullpen), as there is still the chance that the Cardinals hope he can bring some of that newfound velocity to the rotation. If that is the case, it is likely that Rosenthal would start the year in Triple-A polishing up his secondary pitches before joining the big league rotation sometime later in the summer. If not, he could start the year in the majors as one of the Cardinals' primary setup men, and possibly become one of the best in baseball.
Michael Olmsted, RHP, Milwaukee Brewers - Olmsted, 6-foot-7 and 245 pounds, has never pitched above Double-A and turns 26 in May. A ninth-round pick by the Mets in 2007, his past also includes injuries such as Tommy John surgery as well as a trip to Japan, where he also pitched in the minors. Between Salem of the Carolina League and Double-A Portland in the Red Sox system, Olmsted impressed with his stuff (consistently touching 97 mph with his fastball) and his stats (59.1 innings, 36 hits, 10 earned runs, one home run, 92:15 K:BB) in 2012. He was snatched away from the Red Sox this offseason as the Brewers, who watched their bullpen throw their season away in 2012, put him on their 40-man roster and signed him to a minor league deal.
Olmsted is probably the deepest sleeper on this list based on his lack of experience against top competition, but he really looked ready at the end of 2012 and if he gets the opportunity in the majors I expect him to run with it if he stays healthy. He's definitely a guy to watch and see if he makes the team out of spring training, and Olmstead could be a big part of turning the Milwaukee bullpen back into a strength.
Bryan Morris, RHP, Pittsburgh Pirates - Morris, a former first-round pick with the Dodgers, actually came to Pittsburgh in the Manny Ramirez trade in 2008. He was 21 years old and a starter then, and he's 25 and a reliever now after giving up starting in 2011. Morris, who battled a litany of injuries in the past including Tommy John surgery, possesses a low-to-mid-90s fastball with a ton of sink that produces a lot of groundballs and strikeouts (79 in 81 innings at Triple-A). He throws both a curveball and a slider, but the slider seems to be his weapon of choice whereas his curveball is mostly a show-me pitch. His changeup is just a fringe pitch.
If Morris continues to work down in the zone with his stuff, he should continue to miss bats and get a ton of groundballs in the majors. Even if they do get the ball in the air against him, PNC Park can be accommodating in this way. The only questions for Morris are if he can maintain his health and get an opportunity. He figures to have a role somewhere in the Pirates' bullpen to start the season, but it could even be a late-inning role if closer Joel Hanrahan is traded at some point.
J.J. Hoover, RHP, Cincinnati Reds - Traded by the pitching-rich Braves for Juan Francisco, this converted starter dominated while coming out of the bullpen at Triple-A (37 innings, 15 hits, five earned runs, one home run, 55:12 K:BB) and in the majors (30.2 innings, 17 hits, seven earned runs, two home runs, 31:13 K:BB) for the Reds in 2012. Hoover flew under the radar in the Atlanta organization looking like a back of the rotation starter, but since he brought his fastball (92-94 mph), slider, and changeup mix to the bullpen it looks like he can be a late-inning option. Not only does he have good stuff, but he really knows how to use it as it is rare to see him walking batters or giving up home runs.
Hoover's biggest problem at the moment in terms of fantasy value is where he fits in the Reds' bullpen, which is loaded. Even with Aroldis Chapman heading to the rotation, the Reds have Jonathan Broxton, Sean Marshall, Jose Arredondo, and Sam LeCure. There will be openings as the season goes along, but he is one to watch if he makes the club on Opening Day.
Phillippe Aumont, RHP, Philadelphia Phillies - Amount was the most highly touted player on this list entering the 2012 season as he was ranked as a top-five Phillies prospect by Baseball America and has been regarded for a long time as a talented young arm. Another converted starter, Aumont has pitched out of the bullpen in the minors since 2011 and even debuted in the majors as a reliever in 2012 (14 innings, 10 hits, six earned runs, 14:9 K:BB). Aumont gets it done with a big fastball (94-96 mph) and power curveball. He can miss bats with both pitches and he is capable of dropping his curveball in for a called strike when necessary. Control has always been an issue for Aumont, who stands 6-foot-7, as he's always struggled with his mechanics.
Aumont's control is the biggest weakness any of these pitchers listed has and yet because of his prospect status, ability to miss bats, and openings in the Phillies' bullpen even after the addition of Mike Adams, he definitely has a chance to make an impact in leagues that value holds. There will be times when he is really fighting his control issues, but ultimately there is upside here in deeper formats.
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