Sergio Mendoza stopped Ricardo Sandoval in the fifth round to claim flyweight world honours at Chicago’s Wintrust Arena, dropping the defending champion three times in an upset that ended Sandoval’s seven-fight winning run. The Ring reported that Mendoza won the WBA and WBC 112lb titles, while the WBC confirmed the Mexican as its new flyweight champion after the referee intervened during the fifth round.
Mendoza had entered the bout as a late replacement after Puerto Rico’s Oscar Collazo withdrew from his scheduled title challenge because of a rib injury sustained in training. The opportunity arrived roughly three weeks before the contest, according to The Ring, but Mendoza made immediate use of it against an opponent who had been strongly favoured.
Sandoval had won the crown from Kenshiro Teraji in July 2025 and was seeking to defend it in Chicago. The WBC said Sandoval arrived on a seven-fight winning streak, while The Ring reported that he was a 7-1 favourite with DraftKings. Mendoza’s victory therefore altered the expected outcome of a fight in which Sandoval had been defending his position at the top of the division.
Three knockdowns changed the contest
The decisive moments came in two separate rounds. Mendoza first put Sandoval down twice in the second, establishing an early advantage over the champion. The Ring reported that a right hook sent Sandoval down with 1:39 remaining in that round, before a left uppercut produced a second knockdown 18 seconds before the bell.
Sandoval recovered sufficiently to make the middle rounds competitive, but he could not withstand Mendoza’s attack in the fifth. A counter right hook dropped Sandoval to his gloves and one knee with 1:40 left in the round. Referee Mark Nelson stopped the contest at 1:46 of the fifth after Sandoval remained under pressure and appeared hurt.
The three knockdowns provide a straightforward measure of Mendoza’s control in the pivotal exchanges: two came before the halfway point of the scheduled 12-round fight and the third directly preceded the stoppage. Sandoval rose quickly after each of them, The Ring reported, but the repeated damage left him unable to continue when the final attack arrived.
The WBC similarly said Mendoza sent Sandoval to the canvas three times before the fifth-round knockout. Its account described the result as a major upset and confirmed that the contest was staged at the Wintrust Arena.
Mendoza responds after April defeat
The result was a sharp reversal from Mendoza’s previous appearance. The Ring reported that he had been knocked out in the second round by IBF junior-flyweight champion Thanongsak Simsri in Tokyo on 13 April, when competing at 108lb. Against Sandoval, Mendoza returned at 112lb and improved his professional record to 28 wins and one defeat, with 24 knockouts.
After the fight, Mendoza said that making 108lb had affected him and maintained that flyweight was his natural division. That assessment remains his own explanation, but the move back to 112lb coincided with a WBC title win after his preceding contest ended inside the distance.
Sandoval’s record moved to 27 wins and three defeats, with 18 knockouts, according to The Ring. The publication also reported that it was the first stoppage defeat of his 30-fight professional career, underlining the significance of Mendoza’s finish rather than simply the change of champion.
For Mendoza, the immediate competitive consequence is clear in the organisations’ accounts: he leaves Chicago with championship status at flyweight. The WBC named him its 112lb titleholder, while The Ring reported that the victory also secured the WBA belt. The late call-up became a title-winning night, built on a second-round breakthrough and completed by the fifth-round intervention.