Major League Baseball suspended outfielder Marlon Byrd 50 games for testing positive for Tamoxifen, a performance- enhancing substance.

Byrd, who is a free agent, spent time with the Cubs and Red Sox this season. In 47 combined games, Byrd hit .210 with one homer and nine RBI.

"I made an inexcusable mistake. Several years ago, I had surgery for a condition that was private and unrelated to baseball," Byrd said in a statement. "Last winter, I suffered a recurrence of that condition and I was provided with a medication that resulted in my positive test. Although that medication is on the banned list, I absolutely did not use it for performance enhancement reasons.

"I am mortified by my carelessness and I apologize to everyone who loves this game as I do. I will serve my suspension, continue to work hard and hope that I am given an opportunity to help a Club win later this season."

He will be placed on the restricted list for the duration of his suspension, which will begin immediately.