Dominick Cruz underwent another major knee surgery this past week, and it’ll likely further delay his return to the octagon.

Trainer Eric Del Fierro today told MMAjunkie.com (www.mmajunkie.com) that Cruz’s anterior cruciate ligament (ACL) was replaced after his body rejected one from a cadaver.

The UFC bantamweight champion is in Los Angeles today to meet with a doctor who will give him a timeline for his return, DelFierro said, though he estimated it could set the fighter back another six to nine months.

Cruz (19-1 MMA, 2-0 UFC) underwent corrective surgery in June after tearing his ACL in preparation for a rematch with Urijah Faber, who coached opposite him on “The Ultimate Fighter 15.” The two were scheduled to meet at UFC 148 on July 2, but Cruz was forced out of the fight, and Renan Barao went on to beat Faber to claim an interim title at UFC 149.

Del Fierro said Cruz’s ACL was replaced, as well as his MCL, which had been torn prior to a fight with Charlie Valencia in 2008.

Following several months of recovery, the MCL held while the ACL did not.

“He’s pissed and disappointed,” Del Fierro said. “But I think he’s doing better now. Once he talked to the doctor and found out what was going on, he felt much better.”

The trainer said Cruz’s training was advancing with the approval of his doctor and physical therapist, but he had not been cleared to prepare for a fight.

Meanwhile, Cruz hoped to return in early 2013 but couldn’t provide a date.

Cruz most recently stepped into the cage in October 2011, when he outpointed Demetrious Johnson to defend his title, which he also defended against Faber at UFC 132.

This past month, UFC President Dana White said he would offer a fight to Barao, possibly against Michael McDonald, despite the champ’s stated preference to wait for Cruz’s return. Barao coach Andre Pederneiras said late this past month that he had yet to receive an offer but would welcome a fight in early 2013.

For more on the UFC’s upcoming schedule, stay tuned to the UFC Rumors section of the site.