OAKLAND -- Bartolo Colon's recent struggles have prompted a debate about the righty's need for extra rest. The A's believed their 14-game winner could get by without it, until they had no choice but to give it to him.

Instead of making his scheduled start on Sunday, Colon will be placed on the 15-day disabled list with a left groin strain, an injury that initially surfaced during his Friday flat ground session. Lefty Tommy Milone will be recalled from Triple-A Sacramento to start in his place against the Indians.

"Yesterday was the first time he felt it," manager Bob Melvin said. "He came in today and it was sore again. Probably the prudent thing to do is not push him too much here and give him these 15 days off and see where we go from there. But to be able to have a guy like Tommy Milone to call on and pitch tomorrow is quite the luxury."

For much of the season, Colon has been considered the club's most reliable starter, though his past two outings would suggest otherwise, leading to the belief that the 40-year-old is tiring. He's given up a combined 10 earned runs in his past two starts, spanning just 6 2/3 innings, after surrendering just as many in his previous 49 1/3 innings over seven outings.

Colon's DL stint will be retroactive to his last start on Tuesday, meaning the A's could have him back in less than two weeks barring any setbacks.

"He wants to make every start that he can," Melvin said. "Based on the fact he's had a great season for us and is a guy that we've leaned on pretty hard and has 14 wins to this point, it's not easy. You always want him to be able to pitch, but maybe with his age and so forth, a little break at this point might be good for him."

Milone, meanwhile, hasn't pitched for the A's since Aug. 2, when he was tagged for six runs on nine hits in just 3 2/3 innings against the Rangers, marking yet another shaky outing that led the A's to option him to Triple-A Sacramento.

While there, Milone made two starts, giving up just two earned runs over 10 1/3 innings, striking out 15 next to just one walk. Now, he has another chance to prove himself at the big league level again.

"Really, it was command, just throwing quality strikes," Milone said. "When I'm able to do that, I've been successful. I was able to do that while I was there, and it was a less stressful environment, so it made it a lot more comfortable to work on those things."

"He was working on his breaking ball, his changeup again, and kind of getting back in sync with what we've seen for the better part of two years," Melvin said. "He feels pretty good about where he is right now."