The UFC appears to have lost another huge star as former UFC heavyweight champion and WWE megastar Brock Lesnar informed the UFC Tuesday that he will be retiring from the sport of mixed martial arts. Lesnar is currently serving a one-year suspension for a failed drug test.

As reported by USA Today, the news about Brock Lesnar’s retirement was broken by a UFC official, which also removes him from the USADA drug-testing pool. As noted by the report, should Lesnar decide to jump back into the Octagon, will have to serve the remainder of his one-year suspension retroactively. The 39-year-old tested positive for clomiphene, which overturned his UFC 200 win against Mark Hunt to a no contest.

Brock Lesnar’s announcement adds to the UFC’s woes. The company, which was purchased by WME-IMG last year for $4 billion, has struggled so far this year in trying to even come close to the success it enjoyed in 2016. In December, Ronda Rousey was brutally pummeled by women’s bantamweight champion Amanda Nunes in just 47 seconds, likely spelling the end of the former champion’s MMA career. Meanwhile, the UFC’s biggest star, Conor McGregor, continues to flirt with the possibility of fighting Floyd Mayweather Jr. in a boxing match – going so far as to say that his next match will be in a boxing ring.

As noted by veteran MMA reporter Chad Dundas of Bleacher Report, 2017 has been devoid of the stars that powered the UFC’s events in 2016, with names like Valentina Shevchenko, Dennis Bermudez and Germaine de Randamie having been tapped to headline this year’s events thus far. Apart from the absence of Brock Lesnar, Ronda Rousey, and Conor McGregor, the UFC has yet to schedule fights for second-tier stars like Jon Jones (still serving a suspension until July), Nate Diaz and, potentially, Georges St. Pierre.

“The UFC fired a lot of promotional bullets to make 2016 its most profitable year ever,” Dundas said, which included the surprise inclusion of Brock Lesnar at UFC 200. “During the first half of last year, the company was for sale after all, and during the second, executives may have been scrambling to justify the $4.2 billion WME-IMG paid to acquire it in July.”