The WBA and WBC flyweight champion was supposed to defend his titles against Oscar Collazo next month, but he pulled out last week after a rib injury during training.

Sandoval (27-2, 18 KOs) is now set to face Sergio Mendoza (27-1, 23 KOs) at Wintrust Arena in Chicago, Golden Boy Promotions announced Friday. Their bout will serve as the co-feature before the main event between Floyd Schofield (19-0, 13 KOs) and Lucas Bahdi (20-0, 15 KOs) for the vacant WBA lightweight title.

“I’m very excited to still be fighting in Chicago and to have the opportunity to defend my titles for the first time,” Sandoval said in a statement. “I’ve been training extremely hard and I’m ready to put on a great performance. I know the fans can expect an exciting fight, and I’m looking forward to stepping into the ring and giving them a show.”

Sandoval, of Rialto, California, has been snakebitten by opponent injuries scrapping significant fights ever since won his 112-pound titles by beating Kenshiro Teraji via split decision in July 2025.

Sandoval, 27, was supposed to face Galal Yafai on June 6 as part of a Matchroom Boxing card in the UK, but the fight was scrapped once Yafai fell injured.

Collazo is The Ring, WBA and WBO champion at 105 pounds and ranked No. 10 on The Ring’s pound-for-pound list. He was supposed to jump two weight classes for the slugfest against Sandoval before bowing out with an injury.

Mendoza, from Hermosillo, Sonora, Mexico, will make his United States debut against Sandoval. He lost by second-round stoppage against 108-pound IBF champion Thanongsak Simsri in April in Japan.

But Mendoza, 26, is right back into a meaningful matchup despite the defeat.

“I want to thank the people who made this fight possible,” Mendoza said in a statement. “I’m going to leave my soul in the ring to become world champion.”

Also set to be featured on the undercard of the Golden Boy and MVP co-promoted show are a pair United States Olympians in lightweight Jahmal Harvey (4-0, 3 KOs) and heavyweight Joshua Edwards (7-0, 6 KOs).

Manouk Akopyan is The Ring’s lead writer. Follow him on X and Instagram: @ManoukAkopyan