The Oakland Athletics' bid to snap a six-year playoff drought was dealt a severe blow on Wednesday as former Cy Young winner Bartolo Colon was suspended 50 games by Major League Baseball after testing positive for testosterone.
The suspension of Colon, who has a team-leading 10 wins this season for an Oakland squad that is sitting a half game out in the American League wild-card race, is effective immediately, MLB said in a statement.
A native of the Dominican Republic and the American League's Cy Young winner in 2005 as top pitcher, Colon was hit with the ban for violating MLB's drug prevention and treatment program.
"I apologise to the fans, to my team mates and to the Oakland A's," Colon said in a statement released by the players' association.
"I accept responsibility for my actions and I will serve my suspension as required by the joint drug program."
Colon will miss Oakland's final 40 games of the 2012 regular season and the first 10 games of the postseason should his team qualify. Any remaining games of the suspension would be served in a future season.
Oakland are second in the American League West division, five games behind the pacesetting Texas Rangers, but could also reach the playoffs if they can catch either the Tampa Bay Rays or Baltimore Orioles in the wild-card race.
The 39-year-old Colon, an All-Star with the Cleveland Indians in 1998 and the Los Angeles Angels in 2005, is the second player to be suspended by MLB over a positive doping test in a week.
San Francisco Giants' All-Star outfielder Melky Cabrera was also banned for 50 games without pay last Wednesday after testing positive for testosterone.
"The Oakland Athletics are disappointed to learn of today's suspension of pitcher Bartolo Colon," the team said in a statement.
"The organisation 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."
Colon is the fifth MLB player suspended this year due to a positive dope test, following Cabrera, Philadelphia infielder Freddy Galvis (50 games), free agent outfielder Marlon Byrd (50 games) and San Francisco reliever Guillermo Mota (100 games).
Colon, who spent last season with the New York Yankees, is 10-9 with a 3.43 earned-run average (ERA) in 24 starts this year and was 4-1 with a 1.57 ERA in his past five outings.