Jaime Munguia has reportedly tested positive for a banned substance following his rematch victory over Bruno Surace.

Munguia, the former WBO super welterweight world champion, returned an adverse analytical finding for an exogenous origin of testosterone metabolites in a urine sample taken by the Voluntary Anti-Doping Association around Munguia’s fight with Surace on May 4 in Riyadh, Saudi Arabia, according to Ring Magazine.

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Munguia will likely face a suspension from the British Boxing Board of Control, under whose jurisdiction the bout took place, unless his B sample tests negative. The Mexican boxer has 10 days to request analysis of his B sample.

Additionally, Munguia’s 12-round unanimous decision win over Surace will likely be overturned to a no-contest.

Surace was a frontrunner for Upset of the Year and Knockout of the Year when he brutally dispatched Munguia in the sixth round of their first fight last December. Munguia, a -2500 favorite, was seemingly miles in front on the scorecards but walked into a counter right hand from Surace in the final minute of the sixth and ultimately failed to beat the 10 count.

For the rematch, Munguia teamed up with renowned boxing trainer Eddy Reynoso. Reynoso is best known for being the longtime coach of Saul “Canelo” Alvarez, who himself defeated Munguia in May 2024.

Munguia boxed a disciplined fight to take a comfortable unanimous decision over Surace in their second meeting, which was the co-feature to Alvarez’s undisputed title win over William Scull. Instead of being wild and reckless, as he had been in previous fights, Munguia was patient behind his heavy jab and worked on creating openings to Surace’s midsection.