Cleveland Indians outfielder Marlon Byrd has been suspended for 162 games after failing a drug test for a second time.
Major League Baseball announced on Wednesday that Byrd had tested positive for Ipamorelin, a growth hormone.
Byrd said he will not appeal the penalty, adding in a statement that he did not knowingly take the performance-enhancing drug.
"After an extensive investigation by my lawyers and an independent chemist, it was concluded that the most likely source of Ipamorelin was a tainted supplement," the statement read.
"I alone am responsible for what I put in my body, and therefore, I have decided for forgo my right to an appeal in this matter and accept the suspension.
"I apologise for any harm this has caused the Cleveland Indians, Indians' fans, my team-mates, and most importantly, my family."
His first offence came in 2012 when he tested positive for Tamoxifen and served a 50-game suspension. MLB has established a three-strikes policy, so a third positive test result for Byrd would result in a lifetime ban.
The 38-year-old joined the Indians in the off-season and is hitting .270 with five home runs and 19 RBIs.
Byrd's suspension will mean the Indians have lost a second outfielder after Abraham Almonte was suspended for 80 games in February after he tested positive for boldenone.