Dmitry Pirog ruptured a disc in his back while training, forcing him to pull out of an Aug. 25 HBO main event against middleweight titlist Gennady Golovkin, promoter Artie Pelullo told ESPN.com on Thursday.
Pirog was training in the mountains in his native Russia, preparing for the bout, when he suffered the injury this past weekend, Pelullo said.
"He trains with big tires and a sledgehammer, and he hits the tire with the sledgehammer, and he was doing that and he ruptured a disc in his back," Pelullo said. "He was up in the mountains where he always trains. Everything was going fine. He injured it while doing that workout. Then he flew back to Moscow and saw a specialist. He wanted to fight but there's no way. He will be out three to four months."
Pelullo said the initial diagnosis is that Pirog (20-0, 15 KOs) won't need surgery.
"They said they don't want to do surgery but they are saying they want him to rest for 30 days and then they will re-evaluate him," Pelullo said.
Pelullo said the card, likely to take place at the Edgewater Casino Resort in Laughlin, Nev., will go on. If a suitable opponent can't be found for Golovkin, who is with K2 Promotions, to defend his title, the promoters and HBO would put together an entirely new main event.
Pirog, who holds a middleweight title, was willing to be stripped of the belt in order to face Golovkin because he wanted to fight in America on HBO.
Knowing he evenutally would be stripped, Pirog accepted the fight anyway, even though he had been ordered to fight interim titlist Hassan N'Dam N'Jikam of France.
"This is the first time Dmitry has ever been injured in training," Pelullo said. "He is totally, totally upset. He thought this fight was his big coming-out party. He was willing to give up his title to fight on HBO. So he's not going to be the WBO champion anymore and he's not on HBO right now because of the injury. But HBO knows he was giving up the title to be on the network, so when he's ready to fight again, I'm sure HBO will put him back on against the right opponent because he will fight anybody, and they know that."
Pirog, 32, has fought once in the United States -- in July 2010, when he knocked out Daniel Jacobs in Las Vegas in the fifth round in an upset on an HBO PPV undercard to win a vacant title.
Pirog has made three title defenses, all in Russia.
Golovkin (23-0, 20 KOs), 30, a 2004 Olympic silver medalist for Kazakhstan, has made four title defenses and, like Pirog, has wanted to fight in the United States on HBO.
The Aug. 25 co-feature remains intact and will pit former junior middleweight titlist Sergiy Dzinziruk (37-1, 23 KOs), 36, of Ukraine, against Puerto Rican prospect Jonathan Gonzalez (15-0, 13 KOs), who turns 23 in two weeks. The fight will be Dzinziruk's first since he moved up to middleweight in March 2011 to challenge lineal champion Sergio Martinez and was dropped five times in a one-sided eighth-round knockout loss.