Josh Barnett may have won his arbitration battle with USADA, which would clear him to be able to fight in the UFC immediately, but it will be at least six months before he will be allowed in the cage.

Barnett, after receiving his provisional suspension from USADA in December 2016 for a positive test for the banned substance ostarine, pulled himself out of the USADA drug-testing pool. That decision, though he never announced it publicly, is treated the same as the announcement of his retirement.

MMA Weekly was the first to report on this development.

By making that decision, he would have to put himself back in the testing pool and test clean for at least six months before being eligible to fight again in the Octagon, per the UFC anti-doping policy. At this point, the earliest he could fight, if he was to put himself back in the pool, would be the end of September. As of today, he had not informed USADA that he was re-entering the testing pool.

”Josh took himself out of the pool on December 14, 2016,” USADA spokesperson Brad Horn told MMA Fighting.

USADA then confirmed to Barnett on Dec. 19, 2016 that it considered him a retired fighter and removed him from the pool.

”He has yet to reenter and would be subject to the six-month waiting period, as such,” Horn said.

Barnett was informed on March 23 that an independent arbitrator ruled in his favor, giving him a public warning in his doping case. USADA could not suspend him since he was able to prove he did not knowingly cheat, that his positive test came from a tainted supplement and that he had already been kept out of action for 15 months.

Barnett had kept a small amount of every supplement he had taken for the past several years for the very reason of having a defense in case he tested positive. He said he did it because in 2009, when he had tested positive in California, he believed it was due to a tainted supplement, but he hadn’t kept small amounts of any of his supplements and thus was unable to prove that to be the case.

He said that last May he was able to produce evidence of a supplement that had Ostarine. However, USADA was pushing for a suspension, and Barnett took the case to arbitration.

Barnett, upon finding out he won his arbitration battle, didn’t have an immediate timeline of when he wanted to fight again. But, at 40 years old, time is not on his side regarding extending what is already a lengthy layoff.

Barnett has had one of the longest active careers in MMA, as he began fighting 21 years ago. He defeated Randy Couture on March 22, 2002, in Las Vegas to win the UFC heavyweight championship, only to be stripped of the championship due to a positive drug test.

For the next several years, he made his name in Japan, both as a pro wrestler with New Japan Pro Wrestling, and fighting with Pride, where he was one of the company’s top heavyweight stars. He returned to the UFC after 11 years away with a win over Frank Mir at UFC 164 and went 3-2 prior to his suspension.