The suspension begins with the Rockies game at Arizona on Monday night, the commissioner's office said.
Piedra, who was recalled from Triple-A Colorado Springs of the Pacific Coast League on Wednesday and sent back down the next day, is the second player to be publicly identified under the major leagues' tougher rules. Tampa Bay outfielder Alex Sanchez (search) was suspended for 10 days last Monday.
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.