Tito Ortiz will enter the cage for what he says will be the final time on Saturday when he faces Chael Sonnen at Bellator 170 in Los Angeles. Dave Mandel/Sherdog

After nearly 20 years of professional cage fighting, Tito Ortiz is more than ready to call it a career.

Ortiz (18-12-1) takes on Chael Sonnen on Saturday, at Bellator 170 in Los Angeles (9 p.m. ET, Spike TV/ESPN Deportes/ESPN3). The bout will take place two days before his 42nd birthday, and Ortiz has repeatedly said it will be his last.

Retirement is not always definitive in mixed martial arts. History has shown it's hard for fighters to stay away, especially those with the ability to command big paydays. Ortiz would know, having retired in 2012, only to come back in 2014.

But Ortiz, who did not fight at all in 2016, says he is "100 percent" sure Saturday will be his final fight. And speaking to ESPN's 5ive Rounds podcast, the former UFC champion admitted he has already felt some scary physical effects from a professional fighting career that began at UFC 13 in 1997.

"I've had over 25 concussions, over eight surgeries" Ortiz said. "Sparring is probably the hardest thing in training -- getting punched in the face, concussions. I don't want any type of brain damage.

"I don't know if you guys got the opportunity to watch the 'Concussion' movie with Will Smith. That's scary. It's a scary feeling. Over this last year, I got a few small symptoms like that -- forgetful, takes me a second to think about some ideas. I don't want that to happen [long term]. I want to make sure I walk away at the right time. Now is a good time."

Still fighting out of Huntington Beach, California, Ortiz has gone 2-1 since signing with Bellator MMA in 2014.

He shocked many observers by submitting former middleweight champion Alexander Shlemenko in his promotional debut in May 2014. Ortiz fought former light heavyweight champion Liam McGeary for the 205-pound title in September 2015 but lost via decision.

Ortiz, who fought for the UFC from 1997 to 2012, says he has enjoyed being with Bellator, a company that "gave [him] respect."

PODCAST: 5ive Rounds Brett Okamoto and Brian Campbell chat with Chael Sonnen and Tito Ortiz ahead of Bellator 170. Listen

Sonnen (28-14-1) is making his Bellator debut. The 39-year-old is coming off a three-year layoff, which was mostly due to a two-year drug suspension.

Ortiz has brought up Sonnen's doping history several times during the fight's buildup and says his opponent's tendency to look for a "shortcut" will show itself again on Saturday.

"I've known many guys who trained with him, and he takes breaks. He's not able to push himself in the red zone," Ortiz said. "During the fight, I'm going to put him in the red zone. I'm gonna push his mind, body and heart.

"Over the past 14 weeks, I've been doing the same to myself. I would either pass out, throw up or die [in camp]. I threw up probably 30 to 40 times during this camp, I never passed out, and I'm still talking to you right now, so the third one never happened."