Cruz's injury rehabilitation was expected to get him back in action in the first part of next year, but a setback put him on the surgeon's table once again, further delaying his return.
In his absence, the UFC already crowned an interim champion in Renan Barao, and now the 135-pound titleholder will defend his belt.
UFC president Dana White confirmed the news via UFC Tonight on Fuel TV on Tuesday evening.
No date has been announced by the promotion, but sources have indicated when speaking to MMAWeekly.com that a Barao vs. McDonald fight would likely take place in the first few months of 2013.
McDonald has already been out since April of this year when he knocked out former WEC champion Miguel Torres. Following that fight, McDonald had surgery on his hand, but is now back in full training mode and preparing for a fight.
McDonald told MMAWeekly Radio just days ago that he could be ready as early as the end of January, and with Barao sitting out since July, it's likely the pairing will be made sooner rather than later.