Julio Cesar Chavez Jr. was booed and pelted with debris by fans Friday after the Mexican boxer quit following the fifth round of his fight against Daniel Jacobs at Talking Stick Resort Arena in Phoenix.
ESPN's Dan Rafael reported Chavez made "plenty of excuses" after the abrupt finish and accused Jacobs of rule violations "that did not occur."
"I was getting close but got head-butted above the left eye," Chavez said. "Then I had problems because of all the blood. I came over to the corner and couldn't breathe. He elbowed me and head-butted me. Very tough fight. I felt I couldn't go because I couldn't breathe properly. The ref wasn't calling anything.
"I apologize to the fans. I'd love to have a rematch. I got head-butted. He fought a dirty fight, and [the referee] didn't even take a point away. He would have been able to continue doing the dirty work."
His lawyer, Miguel Leff, backed up the 33-year-old veteran's assertion of a broken nose, telling ESPN he'll require a 24-hour hospital stay for reconstructive surgery.
Jacobs said he was disappointed in the lack of focus on his victory, though he understood the fans' outrage was directed toward his opponent, per Rafael.
"I am comfortable with the victory. Obviously, they won't let me enjoy it," he said. "I know they're not mad at me. They're mad at Chavez, but I did my part."
Chavez also quit following the ninth round of a 2015 encounter with Andrzej Fonfara.
He's gone 3-3 over his last six fights after a 48-1-1 start to his professional career. Given two of those three losses have come via throwing in the towel, he could struggle to generate offers for more high-profile bouts.
Meanwhile, Jacobs bounced back from a loss to Saul "Canelo" Alvarez in May with Friday's triumph to move his career record to 36-3. His only defeats since the start of 2011 have come against boxing superstars in Alvarez and Gennady "GGG" Golovkin.
His dominant display against Chavez should move him back toward the title picture in either the middleweight or super middleweight divisions.