The league said Wright tested positive for growth-hormone-releasing peptide 2 (GHRP-2). His 80-game ban will begin in the 2019 season, and he is ineligible to play in any playoff contests in the upcoming campaign.
Wright told the Boston Globe that he can't prove it was unintentional. He failed the test previously in the offseason and told the team a few weeks ago of the positive test while it was being appealed.
"We couldn't figure out how this substance got into my body," Wright said. "But at the end of the day, it's my responsibility. It falls on me. ... I know the truth. People close to me know I wouldn't intentionally do this. Unfortunately, sometimes things get into your system."
Wright started the 2018 season late after he underwent left knee surgery and served a 15-game suspension for violating the MLB's domestic violence policy. He played in 20 games (four starts) last year and compiled a 3-1 record with a 2.68 ERA.
Wright agreed to a one-year, $1.375 million contract with the Red Sox in January to avoid arbitration. The 2016 All-Star selection has a 24-15 record with a 3.77 ERA in his six-year MLB career.