Niemann, 30, competed with Roberto Hernandez for the fifth spot in the Rays' rotation this spring. Hernandez earned the job and Niemann was sent to the bullpen.
Unfortunately for Niemann, the rigors of being prepared for daily work took a toll on the right-hander's shoulder. He went on the 15-day disabled list on Friday due to right shoulder soreness.
Niemann is 40-26 with a 4.08 ERA in 97 appearances (92 starts), all with Tampa Bay. Contractually, he is under the team's control through 2014.
Bill Chastain is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.