Raymundo Beltran's career has run the gamut, from being a journeyman, to working as a noted sparring partner of Manny Pacquiao, to being a tough contender, and, ultimately, to a short spell as a world titleholder.

Now into his 20th year as a pro, even Beltran himself is surprised with his longevity in boxing.

"No, I never imagined it," said the 37-year-old, who made his professional debut in 1999. "I never thought I was going to do it for so long, even at this age."

Beltran, who's challenging IBF lightweight titleholder Richard Commey on Friday at the Pechanga Resort Casino in Temecula, California (ESPN and ESPN Deportes, 10 p.m. ET), has long ago settled into his role as a grizzled veteran of the game, one who has seen it all. The kind of perspective he has in the sport of boxing can be gained only through experiences, both good and bad. At times, his relationship with the sport, or at least the business of boxing, can be described as love-hate.

"Y'know what, I love the sport of boxing, but I don't see it as I used to, when I was innocent, like in life and everything," Beltran said before a day of training at Wild Card Boxing Club in Los Angeles. "I believed in so many things that I just don't believe in anymore because now, it's a business. But I put myself out of the business and I enjoy the sport -- and I love to win."

Beltran admits he has some regrets about his journey.

"Yeah, I put my heart first, I didn't look at it as a business and I think I let myself down in many situations in life," he said. "That's what I really regret."

Early in 2018, Beltran, who was born in Mexico but resides in Phoenix, was one of the feel-good stories in boxing when he finally captured a world title by defeating Paulus Moses for the vacant WBO lightweight belt. After years of toiling on the club circuit, being the B side for bigger fights and getting the wrong end of dubious decisions against house fighters, he had finally made it to the top of the mountain.

That victory made a showdown against Vasiliy Lomachenko, with a seven-figure payday attached, a real possibility. It was the kind of opportunity he had fought his entire life for, but then, in the interim, Beltran was dethroned in his first title defense by Jose Pedraza in Glendale, Arizona, in what was supposed to be homecoming showcase.

While some of his other losses in the past were debatable, this was clear and at the worst possible moment. He was that close to cashing in on his years of sacrifice.

"I was very frustrated, very bitter, emotional, very hurt," Beltran said. "I don't take anything away from Pedraza -- I felt like I could've won the fight but the circumstances didn't help, at all. It was a learning lesson for me, personally, that I had to make changes in my career."

After the defeat to Pedraza, who ended up parlaying that victory into a fight against Lomachenko -- a unanimous decision loss -- Beltran elected to undergo surgery to repair his left hand, which had been bothering him for a few years.

"After the [Jonathan] Maicelo fight [in May 2015], it was really bad. It didn't get any better from that point. We tried everything, we went to a lot of doctors, a lot of treatments, stem cell stuff -- it just didn't work," Beltran's manager, Steve Feder, told ESPN.

Raymundo Beltran's issues with his left hand didn't stop him from scoring a KO victory over Jonathan Maicelo in 2017. Frank Franklin II/AP

In the past, Beltran felt he had been able to work through his injuries, but not this time. Beltran said he tore a tendon near his wrist area in a sparring session about two weeks prior to the Pedraza bout. He further aggravated the injury in the second round of that fight.

Feder admits that if they had somehow gotten past Pedraza despite the injury issues, they would've still faced Lomachenko in 2018.

"We would've taken that fight [even with the injury],' he said. "It was financially the right thing to do."

But with that opportunity off the table, Beltran finally went under the knife, and he returned to the ring Feb. 10. In his first fight back, he stopped the then undefeated Hiroki Okada in Round 9 at the Save Mart Center in Fresno, California.

play 1:17 Beltran stops Okada in ninth round Ray Beltran levels Hiroki Okada with a right hand, then finishes the fight with a flurry to hand Okada his first pro loss.

Having full use of both hands wasn't the only change for Beltran heading into 2019.

For years he was co-trained by the duo of Ernie Zavala and Pepe Reilly, but after the loss to Pedraza, former unified flyweight world titlist Brian Viloria led him into the ring for the Okada fight. Now Freddie Roach is preparing him for this upcoming contest against Commey.

Feder, a close friend of Roach for years, asked the veteran trainer to work with his client.

"If it ends up being that the corner can make a difference, that's the guy I want in the corner," Feder said. "This camp has been great, he's in the ring with Ray and they're talking through things. It couldn't have gone better, Ray's happy."

Roach didn't need to be sold too hard to add Beltran to the fold, since Beltran provided quality sparring for Pacquiao -- who was trained by Roach -- at Wild Card for years.

"He trains really hard, his legs are steady, I don't see any signs of him being shot or anything like that. He's still fresh, he's doing good," Roach said.

In Commey, they are facing a physically formidable fighter who has heavy hands. But unlike Pedraza, he isn't nearly as shifty or as mobile inside the ring. It's an easier style to decipher, but perhaps a more punishing style to deal with.

"He's a very strong guy, but Ray should be able to outbox him, easily, I feel," Roach said. "Just use the jab and set things up."

Of course, that's easier said than done, especially at Beltran's advanced age. For his part, he feels this camp has prepared him well and he feels good going into the fight.

Raymundo Beltran, left, lost his title in a unanimous decision against Jose Pedraza in August, 018. Mikey Williams/Top Rank

"I'm confident, because I believe in myself," Beltran said. "I'm here at the gym and I'm sparring with all the tough guys, guys way younger than me, top kids, and I can still go good. That tells me I'm still competing."

After seeing the Lomachenko fight slip away, this fight is also likely to be Beltran's final opportunity to remain relevant on the world-class scene, and he said winning this particular world title would have more meaning. In Commey, ranked No. 5 at 135 pounds by ESPN with only two losses in close decisions, Beltran sees a chance at proving he still has what it takes to hang with the best the world has to offer.

"I believe I'm going to win the fight," Beltran said. "Richard Commey is a tough fighter. I'm more excited to fight Richard Commey than for the world title, because you can fight for a belt against nobody and you don't get much credit. Yeah, you're world champion, but who did you take it from? At the end of the day it's about who you fight. So I'm excited to fight Richard Commey."