Martinez exited Wednesday's start against the Royals with a left mid-back strain, Jeff Jones of the Belleville News-Democrat reports.
The veteran right-hander exited in line for the loss during the sixth inning after surrendering eight runs on nine hits with three strikeouts and two walks. It was a disastrous performance in potentially Martinez's final start of the regular season, and it was made worse by the injury. The 29-year-old lines up to pitch Monday against Detroit if those make-up games are deemed necessary, but his availability is up in the air with the severity of the back strain unclear.