The 39-year-old right-hander was 10-9 with a 3.43 ERA in 24 starts and was 4-1 with a 1.57 ERA in his past five outings. He leads the A's in wins, innings pitched and starts.
Oakland, 67-56, has 39 regular-season games remaining on its schedule after Wednesday's win vs. the Twins. Barring rainouts, Colon will miss those games and the first 10 games of the postseason if the A's advance that far. If they don't, the remainder of the suspension would be served whenever Colon, eligible for free agency, signs another Major League contract.
"The Oakland Athletics are disappointed to learn of today's suspension of pitcher Bartolo Colon," the team said in a statement. "The organization fully supports Major League Baseball's Joint Drug Prevention and Treatment Program and its efforts to eliminate performance-enhancing substances from our game. Per the Basic Agreement, the A's will have no further comment."
Oakland entered Wednesday's action a half-game behind Baltimore for the second Wild Card spot in the American League. Colon had been scheduled to pitch Thursday at Tampa Bay. He will be replaced by Tyson Ross, who was recalled from Triple-A Sacramento.
"The fact that someone gets popped like that, no one expects that," Ross said. "He's been a good influence on me. We'll look to [Brandon] McCarthy now."
Colon, the American League Cy Young Award winner in 2005 when he went 21-8 for the Angels, was in his second year after missing the 2010 season following elbow surgery. He underwent a stem-cell procedure, reportedly reviewed by MLB, and made a comeback last season with the Yankees, going 8-10 with a 4.00 ERA.
"We have to look at this game and tomorrow's game," Beane said. "The news filtered out about 10:30 this morning, but we have a game to play and I hope the game itself will become the focus."
The A's signed him as a free agent in January. The 10 wins were his most since his Cy Young season and his ERA was the lowest since 2002, when he pitched for the Cleveland Indians and Montreal Expos.
"I have not spoken to Bartolo," A's manager Bob Melvin said Wednesday. "It is what it is. We certainly don't support the actions."
Brett Anderson's return Tuesday from Tommy John elbow surgery may prove to be fortuitous. The left-hander pitched seven innings in a winning effort in his 2012 debut.
"It's shocking," Anderson said. "A tough break either way. It's something you never expect. You don't really know if people are doing things."
"You don't know at the time," Melvin said. "We were targeting and excited about [Anderson's] return and I don't know if you can ask for any more than that. I do think that is a boost, getting another top-of-the-rotation guy back."
Five Major Leaguers have been suspended this year for positive tests in violation of the drug program. In addition to Cabera, Giants reliever Guillermo Mota was suspended for 100 games in May following his second career positive, Phillies infielder Freddy Galvis and free-agent outfielder Marlon Byrd (most recently with the Red Sox) were each suspended for 50 games in June.
"We're all disappointed, not just for the Giants and A's, but for baseball," Beane said. "We're fortunate to have depth in starting pitcher and it's time to rely on that depth."