Oswalt was taken out of Sunday's start in Tampa Bay after two innings with elbow soreness. He gave up four runs on six hits in those two innings, including home runs by B.J. Upton (who ended up hitting two more off Martin Perez) and Jose Molina, in a 6-0 Rays' win.
Sunday was Oswalt's first start since Aug. 23 and he's been used as a spot starter since the Rangers acquired Ryan Dempster right before the trade deadline. He was pitching Sunday to give Matt Harrison some rest as the Rangers shuffled the rotation. Scott Feldman is scheduled to start on Saturday.
Oswalt is 4-3 with a 6.29 ERA in 54 1/3 innings since signing with the Rangers near the end of May. He's pitched in 13 games and made nine starts.