Former American League MVP and three-time AL All-Star Mo Vaughn has admitted to using human growth hormone to help recover from a knee injury late in his career.

Vaughn played 12 years in Major League Baseball, primarily with the Boston Red Sox from 1991 to 1998. After two years with the Anaheim Angels, Vaughn sat out the 2001 season with injuries. Anaheim traded him to the New York Mets in December 2001, and as his knee got worse, Vaughn said he began using HGH.

“I was trying to do everything I could,” Vaughn told Ken Rosenthal in a story for The Athletic published on Monday. “I knew I had a bad, degenerative knee. I was shooting HGH in my knee. Whatever I could do to help the process…”

This isn’t breaking news; Vaughn’s name appeared in the Mitchell Report in 2007, saying he bought HGH three times in 2001. This is, however, the first time he’s said it publicly. Former Mets batboy and clubhouse employee Kirk Radomski allegedly provided the hormone to Vaughn, who preferred HGH to steroids because they required a smaller needle.

Vaughn returned to the field in 2002 and hit 26 home runs for the Mets that season, but played only 27 games for the Mets in 2003 as his knee problems continued. He never played a big league game again after that.

Despite his career getting cut short, Vaughn still hit 328 career home runs. He also had a career .293 batting average and .906 OPS.

Mo Vaughn has turned his focus to the Vaughn Sports Academy

With his playing days behind him, Vaughn is now focused on the next generation of baseball talent. He runs the Vaughn Sports Academy where he works with young baseball players, focusing on some of the weaknesses of his own game.

A notoriously bad first baseman and two-time league leader in strikeouts, Vaughn is, as Rosenthal wrote, “a stickler for fundamentals.”

“I find it very, very hard when I see young players today who don’t know what’s going on,” Vaughn said. “I don’t care how talented they are. I don’t understand why we can’t put a bunt down, hit behind a runner, hit the cutoff man.”

Similar to focusing on the fundamentals on the field, the academy keeps things simple off the field.

“We don’t have too much parent involvement. We don’t accept that. We’re not big social-media guys. We really don’t accept that,” he added. “I think everybody respects me because I’m getting to tell you the truth. You might not like it, but I’m going to tell you what it is.”