According to Velasquez's camp, he injured his knee prior to the dos Santos bout but opted to fight anyway.
Things took an even more dramatic turn when an actual video was uploaded on YouTube of the injury occurring during a training session.
Ariel Helwani of MMAFighting.com caught up with the former heavyweight champ to get his take on the situation.
There was a couple of film crews in there filming, and they didn't do it before the [first fight], but they've had it in their possession, so they just decided to do it before this fight.
I have no idea why, and I texted a person and said, 'Hey, it's not cool. You should've let me know if it was okay with me to do that.' It makes me seem like I'm crying about what happened before that fight, when it's just not me.
Velasquez has shown nothing but class following his first round knockout loss to dos Santos.
When asked about the injury, he typically deflects questions and credits dos Santos for being the better fighter that night. It would make little sense for him to support releasing a video of an injury that occurred a year ago.
While the video is still on YouTube, it has been made private and is no longer available to the general public. Some are questioning whether Dethrone, Velasquez's former sponsor, released the video in an attempt to get back at the heavyweight star for signing with Affliction.
According to Velasquez, he still has a great relationship with Dethrone, and he doesn't believe him signing with a different brand was the reason the video hit the web.
The owner of Dethrone, I'm good friends with him still. We still have done stuff after I've signed with Affliction. So, I have no idea. For the person that did send it out, [I feel betrayed], and let him know that.
According to the video, Velasquez fought dos Santos with a torn ACL.
If true, the injury was apparently more significant than Velasquez ever let on, and if the bout wasn't the UFC on Fox headliner, there is a good chance he would've withdrawn from the fight.
Velasquez won't make excuses, but he does admit things may have been different if he wasn't headlining in the UFC's first ever primetime event.
You never know. It was [that serious], but you know, just being a fighter, you're always confident in what you have done, so when the opportunity comes, you want to go out there and fight.
Velasquez is set to face dos Santos in a rematch for the heavyweight title at UFC 155 on Saturday night.
Dethrone has yet to make any comments regarding the video.