OAKLAND -- Right-hander Henderson Alvarez underwent an MRI on his sore shoulder that proved inconclusive, leading the A's to send the results to Dr. James Andrews for further evaluation.
Andrews performed Alvarez's arthroscopic shoulder surgery last July. The 26-year-old righty was pitching in what was expected to be his final rehab start with Triple-A Nashville on Sunday when he experienced soreness.
The setback delays Alvarez's season debut, initially thought to be this weekend against the Yankees, and there's no way of knowing when that time will come.
"He played catch today, felt OK, but no timetable for the next time he'll be on a mound, either in a bullpen or in a game," A's manager Bob Melvin said Wednesday.
That the MRI didn't reveal anything alarming, Melvin said, "does give you some optimism."