One of the best wide receivers in NFL history says he resorted to cannabis to seek solace from his pain—and to avoid getting tangled in the opioid abuse taking place in the locker rooms.

In an interview with Sports Illustrated, former Detroit Lions player Calvin Johnson highlighted how players coped with the beatings they took on the field.

“When I got to the league, [there] was opioid abuse,” he told Sports Illustrated’s Michael Rosenberg. “You really could go in the training room and get what you wanted. I can get Vicodin, I can get Oxy[contin]. It was too available. I used Percocet and stuff like that. And I did not like the way that made me feel. I had my preferred choice of medicine. Cannabis.”

While injuries weren’t the primary reason he retired at the prime age of 30, Johnson took a “super conservative” guess, saying he suffered at least nine concussions as a pro athlete—one for each season he played in the league.

He told Sports Illustrated it became routine.

“Bam, hit the ground real hard. I’m seeing stars; I can’t see straight,” he said. “But I know in a couple minutes I’m gonna be fine. Because I’ve done that plenty of times before.”

Calvin Johnson #81 of the Detroit Lions says he used cannabis to relieve his pain after games.

While the NFL is adopting a number of policies to improve players’ well-being, the inclusion of marijuana in a study looking at alternative medicine has been a hot topic.

But the league’s chief medical officer told the Los Angeles Times he wants more conclusive research. “I think that the science, unfortunately, has lagged behind a lot of the popular opinion and press on this,” Dr. Allen Sills said. “We have a lot more opinion than we do science on the use of marijuana for pain.”

Since setting records while grinding on the gridiron, Johnson has opened his own cannabis dispensary this year and teamed up with Harvard to study how medical cannabis affects chronic traumatic encephalopathy, a degenerative brain disease caused by multiple concussions.

Other football legends like Joe Montana have invested in cannabis firms while Rob Gronkowski and Terrell Davis are tied to companies that sell CBD products.