Subriel Matias delivered an adverse analytical finding for the performance-enhancing drug Ostarine in a VADA test, sources tell The Ring.

Matias’ WBC junior welterweight title defense vs. Dalton Smith on Jan. 10 in Brooklyn, N.Y., is now in jeopardy. Matias has until Dec. 1 to request testing of his B-sample.

The 33-year-old Puerto Rican is The Ring’s No. 2 boxer at 140 pounds. Matias (23-2, 22 KOs) became a two-time junior welterweight titleholder when he scored a thrilling majority-decision victory over Alberto Puello in July in New York on the undercard of The Ring III.

If Matias is eventually stripped of his title upon investigation of the positive test result, expect the WBC to quickly order a vacant title fight between Smith and Puello, per sources.

England’s Smith (18-0, 13 KOs) is The Ring’s No. 7 junior welterweight. Puello (24-1, 10 KOs) is No. 3. The plan called for the winner of Matias-Smith to fight Puello next.

Smith was installed as a slight betting underdog vs. Matias in a virtual coin-flip fight. Matias’ lone defeat came in June 2024 vs. Liam Paro via unanimous decision in a major upset.

Ostarine is the same banned substance Ryan Garcia tested positive for following his win over Devin Haney in April 2024. The New York State Athletic Commission, the same entity with oversight of Matias-Smith, suspended Garcia for one year and overturned the victory to a no-contest.

Ostarine is a selective androgen receptor modulator that attaches to proteins in the body and effectively tells muscles to grow. It is used to aid performance by helping athletes build muscle mass and enhance their rate of fat loss and also to increase stamina and recovery ability.

It has been on the World Anti-Doping Agency's banned list since 2008. In 2022, the organization listed Ostarine as an anabolic agent.

Lucian Bute tested positive for Ostarine in 2016 following a draw with Badou Jack in their WBC super middleweight title fight. The result was changed to a DQ win for Jack.

Amir Khan was handed a two-year ban by UKAD after he tested positive for Ostarine following his sixth-round TKO loss to Kell Brook in 2022.