"Hopefully it's just a muscular thing," Melvin said. "Felt it last time out, so we're going to send him back. He's had some trouble in certain areas before, so we want to make sure we cover our bases. Hopefully we know a little bit more tomorrow about what the results are, and hopefully it's only one turn around."
The A's rotation has been victimized by so many injuries this season, it's almost comical at this point. That they keep winning, anyway, allows for some humor. This is the umpteenth injury to an A's starter this year and third for Cahill, who also missed time with an elbow impingement and an Achilles strain.
Consequently, the A's have used 14 different starters this season. Count reliever Liam Hendriks among them; the right-hander will likely get the nod to open Saturday's matchup with the Rays for his fifth such stint.
Should Melvin need Hendriks before then, he would then select someone else to handle the task. Right-handers Frankie Montas, Chris Bassitt and Aaron Brooks are all candidates to follow the opener and pick up the bulk of innings in the game.
If Cahill misses just one start, his next two could come within the confines of home, where he has a 1.49 ERA. In contrast, he owns one of the worst road ERAs in the Majors: 7.02.
Jane Lee has covered the A's for MLB.com since 2010.