OAKLAND -- The A's won't see Jharel Cotton pitch again this season.
Instead of starting against the Rangers on Friday, the rookie right-hander will be limited to an extended bullpen session before his offseason begins. Cotton underwent an MRI on his pitching elbow Monday that came back clean.
"He's healthy, and we want to make sure he stays healthy," A's manager Bob Melvin said. "It just doesn't seem like it's worth the risk of having him go out there this late in the season, throwing 100 pitches and potentially getting a little bit sore again.
"He feels good right now, and we want to make sure he goes into the offseason feeling as good as he does right now."
Right-hander Raul Alcantara, who has provided scoreless outings in two spot starts this month, will start in Cotton's place Friday. Left-hander Sean Manaea, who was scratched from his previous start with back tightness, will be on the mound in Thursday's series opener at Globe Life Park. Right-handers Daniel Gossett and Daniel Mengden will close out the series.
Cotton struggled to find consistency during his first full big league season, finishing with a 9-10 record and 5.58 ERA. He was routinely bit by the long ball, allowing a team-high 28 homers -- 13th most among American League pitchers.
Other times, he was dominant, particularly during an April 10 start in Kansas City that saw him yield just two hits across seven scoreless innings, leading Hall of Famer Pedro Martinez to say Cotton reminded him of himself.

"There are times when he looks like one of the better pitchers in the league, and other times where he struggles some," Melvin said. "So it's going to be about consistency for him going forward, and he realizes that. It's a consistent maintenance and ritual going into each and every start, playing the mental game a little bit more, and expectation for himself. But I think, at times certainly last year and this year, he's shown that he can dominate, at times. It's just consistently trying to get through an entire season without some of the hiccups he's had."
Melvin also reiterated that Matt Olson (hamstring) and Boog Powell (knee) won't play again this season, while Chad Pinder (concussion symptoms) hopes to see action once more.