Nine days from now, Cain Velasquez will face Fabricio Werdum in a three-round heavyweight fight at UFC 207 in Las Vegas.

That in itself is amazing, considering Velasquez is currently having difficulty standing upright any longer than 10 minutes because of pain in his lower body.

Win or lose at UFC 207, Velasquez (14-2) is scheduled to undergo back surgery Jan. 4, five days after the fight. The procedure will be similar to one Velasquez underwent in February.

Velasquez, 34, is experiencing pain in his right leg because of pressure on his sciatic nerve caused by bone spurs. Earlier this year, pain in his left leg forced him out of a scheduled title fight at UFC 196.

Cain Velasquez has used Cannabidiol, a compound found in cannabis, to help deal with lower-body pain. CBD is not a banned substance under the UFC's anti-doping program during out-of-competition testing. Ed Mulholland for ESPN

"It's an achy pain that goes down your leg, and it gets to a point where if you're standing for 10 minutes, you have to sit down," Velasquez told ESPN.com. "If you're going out for a while, a half-hour, you know it's going to be pretty painful. You have to sit down and take the compression off your back.

"The surgery is basically shaving off some bone to make room for my sciatic nerve. After the last surgery, the doctor said I might be pain-free forever, but knowing how I train and what I do as a fighter, the pain could come back. I didn't really know how long I was going to feel good. It ended up being about a year."

Velasquez, who fights out of San Jose, California, said the pain returned shortly after he started training camp for the Werdum fight.

Velasquez has been forced to pull out of fights multiple times. The option of doing so again was discussed, but ultimately he and his team found a different solution: Cannabidiol (CBD).

Velasquez first used CBD, a compound found in cannabis, before surgery this year and saw good results. When the pain resurfaced, Velasquez turned to a CBD oral spray, and it's aided him through camp.

"It's the only thing that allows me to still train, and I'm not taking a harmful painkiller into my body that I'll later become addicted to," Velasquez said. "I don't know how everyone is going to feel about me saying this, but this is just one of the hard facts we as fighters have to go through. In the past, in the NFL, players have gotten addicted to painkillers. I don't want to be an addict of some sort."

CBD is not a banned substance under the UFC's anti-doping program during out-of-competition testing. Velasquez said he plans to discontinue use at least one week before the fight, in order to stay in compliance with the program. He also plans on receiving a cortisone shot to help with any pain.

The in-competition window is six hours before weigh-ins through six hours after the fight.

When asked what effect these symptoms might have on the outcome of the fight, Velasquez adamantly said he has been able to prepare at a high level. It's a big fight in his career. Werdum defeated Velasquez via submission in a June 2015 title fight.

"As far as preparation, I've done everything," Velasquez said. "I've sparred, wrestled. I'm not missing workouts at all. I've done my conditioning -- everything. I feel great going into this.

"This fight is about getting revenge, and that's why I like it. It's a fight I asked for, and it's a fight I really wanted."

According to Velasquez, the post-UFC 207 procedure will mark the eighth overall surgery of his professional career.

That number has a lot to do with Velasquez's decision last month to publicly align himself with the Mixed Martial Arts Athletes Association (MMAAA), a newly formed fighters' advocates group that also includes Georges St-Pierre, Tim Kennedy, TJ Dillashaw and Donald Cerrone. Velasquez is especially interested in securing long-term health care for retired athletes.

"I could see the changes not happening until after I retire," Velasquez said. "But for me, as long as I'm doing something about it. It's something I really believe in."