The light heavyweight was forced to pull out of his UFC 120 fight against Stanislav Nedkov Friday morning after suffering a knee injury in training on Wednesday.
"Wednesday we were training," Cantwell told MMA Fighting. "It was my last medium day training, just trying to cut weight, loosen up a little bit. I was just having a really, really great training session. Literally, the last five minutes I was rolling -- we did three rounds on pads and two rolling -- literally the last minute, I rolled, hit a move, my foot got caught and torqued my knee and popped my lateral collateral ligament. I couldn't walk. I tried to play it off because there were all kinds of people in the room, like, 'Ah, I got a cramp. I'm done training,' kind of thing."
The 23-year-old was understandably disheartened by the news, especially considering the fact that a string of issues have kept him out of action since September 2009. The Nevada State Athletic Commission refused to clear him to fight at UFC 108 against Vladimir Matyushenko due to an undisclosed reason and he also pulled out of a UFC 116 fight against Ricardo Romero in July.
Cantwell admitted, though, that the disappointing news has yet to sink in.
"To tell you the truth, I really didn't have much to think about it. I was planning on fighting up until this morning, even though I couldn't walk. I was still going to try to duke it out, but then the UFC doctor advised me not to and the UFC didn't want to me to, so, really, I've only had a couple of hours to think about it, and it just kind of sucks, man. Back to the drawing board, I guess. Staying positive will be hard, but you got to do what you got to do.
"It sucks, man. I'm in great shape right now. I should be getting ready for tomorrow and here I am [expletive] talking to everybody, bummed out. It sucks. [I'm in] probably the best shape of my life and I just got to watch it waste away, no reward. I put in three months of hard work and now I don't get to celebrate. It kind of sucks."
Cantwell, who was walking around the hotel lobby without crutches but with a noticeable limp, hasn't decided whether he will attend the event Saturday night at the O2 Arena in London.
"I don't know if I'm going to watch. I don't want to be bummed out, sitting there in the best shape of my life watching other dudes do what I want to do. Not trying to be weird or jealous or anything, but I want to be in there, not out there watching it. We'll see. Maybe."
He also refused to explain why he was not licensed to fight at UFC 108.
"I'm able to talk about it, but I don't really want to, especially now that this has happened, I don't want to get into two things right now.
"It was something new that [the NSAC] didn't know about. Everybody got educated on the whole thing, and it was actually better for the commission, better for me; everybody was educated on the situation. It was no big deal. It's all dealt with."
The UFC doctors told Cantwell that his knee should be completely healthy in approximately a month.
Nedkov will not be competing on the card because there wasn't enough time to find a suitable replacement.