The Oakland A's added more depth to their relief corps on Wednesday, acquiring hard-throwing right-hander Sandy Rosario from the Boston Red Sox for cash considerations or a player to be named later. To make room for Rosario on the A's 40-man roster, Oakland has designated outfielder Jermaine Mitchell for assignment.
Rosario joins the A's from Boston but he has spent his entire pitching career in the Marlins organization. The native of the Dominican Republic was an international amateur free agent signing of the Marlins in 2004 and had remained in their organization until this past October, when he was designated for assignment. Rosario was then claimed off waivers by the Red Sox.
The 6'1'' right-hander was a starter early in his career, but he has been a reliever since the 2010 season. Rosario turned heads in his first season as a reliever by leading all minor league relievers in strike-outs with 125 in 92 innings, mostly at the High-A level. He walked only 17 that season and was rewarded by the Marlins with a big league recall. He made two appearances for the Fish in 2010, allowing six runs in one inning of work.
In 2011, Rosario was a Double-A Southern League mid-season All-Star. His ERA was 4.15, but he struck-out 46 in 47.2 innings and saved 23 games. He would make his Triple-A debut that year, collecting four saves and allowing three runs in 6.2 innings. Rosario made four appearances for the Marlins in 2011, as well, allowing one run in 3.2 innings.
This season, Rosario began the year with Triple-A New Orleans and he was red-hot to start the season. He saved 16 games and posted a 1.04 ERA with a 24:2 K:BB ratio in 26 innings. At that point, he was recalled to the big leagues. Unfortunately for Rosario, he injured a quad after only four appearances with Miami and would spend much of the rest of the year on the DL.
Rosario has good velocity on his four-seam fastball, which generally sits in the 92-94 MPH range and can touch 97. He also has a decent slider that usually sits in the low-80s, and a change-up. His control has been above-average since he became a reliever, although his fastball command can betray him within the strike-zone at times. With the exception of the quad injury in 2012, Rosario has been generally healthy throughout his career.
Mitchell was designated for assignment after spending one season on the A's 40-man roster. A 2006 fifth-round pick of the A's out of UNC-Greensboro, Mitchell had a breakthrough season in 2011 when he hit .332/.430/.530 for Double-A Midland and Triple-A Sacramento. He was the A's co-Organizational Player of the Year in 2011 along with Michael Choice.
Mitchell had major off-season knee surgery before the 2012 season but still managed to play in 108 games for Sacramento in 2012. Mitchell's numbers weren't up to his 2011 levels, however, as he hit .252/.345/.386.
Mitchell has had an up-and-down minor league career, but he has always been one of the most physically gifted players in the A's organization. Mitchell has above-average speed and gap power, as well as solid plate discipline. He is also a good defensive outfielder and can handle all three outfield spots. He will now be exposed to waivers.
Even without Mitchell on the 40-man roster, the A's still have a crowd of players at that position. The A's have eight outfielders on their current roster and that doesn't include Grant Green, who has spent much of the past two seasons playing in the outfield. It wouldn't be surprising to see the A's move at least one more of their outfielders before the start of the season.