Thornton was removed early in his start Sunday against the Rays with right elbow inflammation. He worked around two hits and struck out two over a scoreless first inning before departing.
According to Keegan Matheson of MLB.com, manager Charlie Montoyo was hoping that Thornton would at least be able to cover two innings Sunday in his second start since returning from the injured list, but the right-hander was unable to meet that low bar. The Blue Jays will presumably put him through further tests before deciding his next step, but Thornton could be headed back to the IL since it was elbow inflammation that had previously forced his shutdown earlier this month. Anthony Kay came on in long relief for Thornton and could be a candidate to fill the vacancy in the rotation if Thornton is forced to miss time.