News of the injury to Velasquez surfaced Wednesday when MMAFighting.com reported the 28-year-old heavyweight would require surgery for an undisclosed shoulder ailment, causing him to miss six to eight months.
"We're told he needs surgery but we're trying to get another opinion," said Javier Mendez, Velasquez's trainer. "... We want to make sure that surgery is something that has to happen."
Velasquez will seek second and third opinions next week from doctors in Las Vegas and near his home in the Bay Area.
A recent MRI on his right shoulder revealed the injury was "a lot more severe" than previously thought and showed a 90 percent tear of the rotator cuff. The morning following his first-round win over Lesnar, Velasquez complained about pain in his shoulder.
"We were hoping he'd be back on track," Mendez said. "We gave him two months to rehab. But we did another MRI and it was clear it's torn."
If surgery is required, the Velasquez camp would like it to happen as soon as possible. The heavyweight has trained sparingly since defeating Lesnar, working only on footwork and kicking.
"Cain is not one to sit on his butt," Mendez said. "He'll go stir crazy. He has a lot of ways to learn. He's a great fighter but he still have stuff to improve."
Josh Gross covers mixed martial arts for ESPN.com.