The suspension begins with the Rockies game at Arizona on Monday night, the commissioner's office said.

Tampa Bay outfielder Alex Sanchez was suspended for 10 days last Monday. He said he tested positive from a supplement he bought over the counter before Jan. 15, when it was made a controlled substance.

Selig wouldn't say whether he believed Sanchez. "I want to be kind," Selig said. "He did not fight his suspension, and I'll rest my case on that."

Under the new policy that took effect last month, steroids and other performance-enchancing substances are the only drugs to draw a 10-day suspension. Baseball officials and the players' union agreed they would not disclose the exact substance for which a player tests positive.

The Rockies issued a statement Monday calling the situation "unfortunate."

"As an organization we have, and will continue to support Major League Baseball and its drug testing policies," team president Keli McGregor said.