Jackson, who was the 45th overall pick in the 2010 Draft, was 2-2 with a 4.05 ERA in 33 games, including five starts, for Triple-A Round Rock. Jackson, ranked No. 9 among Rangers prospects by MLB.com, had 71 strikeouts in 60 innings while opponents hit .237 off him, including .185 by left-handed hitters. He had a 3.11 ERA and a .187 opponents batting average as a reliever.
"He's been really good out of the 'pen, especially the last couple of weeks," Rangers general manager Jon Daniels said. "He's always had great stuff -- now we have an opportunity to take a look and see if this is the role that sparks him.