Already among the best in-ring workers in professional wrestling and arguably WWE's biggest singular star, Roman Reigns is reaching his absolute peak as a performer at age 32. 

But if there's one thing about his overall skill set that has yet to reach elite status, it's his ability to cut a confident, lengthy and believable promo on the microphone. 

Reigns, a former college football standout at Georgia Tech who was born Leati "Joe" Anoa'i, admits it's something he works to improve every single day. And if his brief WWE championship feud with AJ Styles in 2016 doubled as Reigns' de facto graduation toward becoming one of the company's best workers, his current program with John Cena just might produce the same result for his mic work. 

After four weeks of viral verbal jousting, which Reigns described as "a learning process," the two superstars are set for a "dream match" on Sunday at No Mercy (8 p.m. ET, WWE Network) in Los Angeles. 

The pair of babyface icons have traded such deeply personal trash talk that seemingly nothing has been off limits. The fact that they aren't close behind the scenes, Reigns said, has prevented any hard feelings from surfacing while the two have continued to shatter the fourth wall.

"I'll be completely honest: Me and John have always been cordial, but I would not say we are close friends by any means," Reigns told CBS Sports during an exclusive interview on this week's "In This Corner" podcast. "There is a business respect, but I think that's what makes this so special that we're truly competing against each other and I think people see that. 

"But it's not like a situation where I'm taking anything he says to heart because I don't really care what he thinks about me. If you care for someone and they knife you, it's going to hurt. It will hurt your feelings and can depress you. But when you don't really care about somebody or their opinion, it doesn't affect you. And that's how it is with me and John."

The timing of such a star-studded feud, typically saved for WrestleMania, is curious for an in-between pay-per-view like No Mercy -- not that fans are complaining. Reigns admits he was excited when he heard a program with Cena was forthcoming, adding that the heavy spotlight that comes with working alongside "one of the greatest of all-time" is exactly what anyone in this business strives hopes to achieve.

"You want to shine, you want to stand out, and you want to be part of something special. And that's what I feel is going on right now," he said. 

Be sure to subscribe to my podcast In This Corner with Brian Campbell to listen to our 25-minute exclusive interview with Roman Reigns along with plenty of WWE analysis each week.

Reigns enters No Mercy fresh off what might be the best promo he has ever delivered in a WWE ring on Monday's episode of Raw. But that was a solo effort, and the best moments of this feud have come when the two have traded barbs in person, which has included pockets of improvisational gold. 

The best example of which came on the Sept. 4 episode of Raw in what served as the second of three straight promo duels between Reigns and Cena. As the 16-time WWE champion was in the midst of tearing Reigns down on the microphone, Cena noticed that the zipper on Reigns' pants was down and called him out on it live.

"The funny thing is, my zipper literally broke like two minutes before I was walking out," Reigns explained on the podcast. "Usually I do a last-minute check. Do I have boogers in my nose? Any like weird hair conditioner on my ears? Is my zipper up? I kind of push and normally you'll check your zipper to make sure the teeth are right in place. I actually pushed right through it. 

"The actual zipper handle popped off, and once that happens, you have to go out there in two minutes. It's not like I'm just wearing trunks or something. I've got blousing straps at the bottom, and I would have to take everything off in order to get new pants on."

Reigns didn't skip a beat upon fielding the insult and responded to Cena's ad-libbed comment by saying, "I busted it actually … big dog." The joke instantly lit up social media.

"John being John, if anything presents itself, which I feel is fair game if it's there to take it, and he did," Reigns said. "Luckily, that's one thing of just over the years going back and forth in locker rooms, I have a quick rebuttal with little things like that. It was just something that, thank God I was ready for it, but really he shocked me in bringing up. I thought I had it closed up the whole time but apparently not. I was peaking at him, I guess."

The war of words between John Cena and Roman Reigns has made for great TV. WWE

While Reigns revealed it felt strange to see Cena to go to that level, he admits it did wonders to spice up their feud. If you can't handle insults in sports entertainment, Reigns said, you'll never be able to handle the physicality. It's a lesson he learned from Fandango during his time in FCW, the company's pre-NXT developmental territory. 

"He was one of the top guys when I first broke in, and he said, 'You have to be a tough guy to run around like a sissy and wear tight pants,'" Reigns said. "I didn't think about it, but it slowly set in like, 'He's right.' He has thick skin and he's willing to do just about anything and he doesn't get embarrassed."   

While the constant trash talk between Cena and Reigns has become the best part of Raw in recent weeks as WWE has noticeably stepped up its creativity to compete for ratings with the NFL, the lack of physicality between the two has been refreshing. It has also raised the expectations for Sunday, when they square off against each other for the first time. 

AJ Styles, a guest this week on a special bonus "In This Corner" podcast episode set to be released late Thursday, believes it's something Cena does better than anybody else. It's also the biggest lesson he has learned since making his WWE debut in 2016 -- the story is what makes the match.

"[Cena] will make you care about that match before anybody steps foot in the ring," Styles told CBS Sports. "That's what it's all about. That's what I learned from John Cena, to tell that story before you ever step into the ring and then capitalize on the athletic ability of both guys in it and now you've got a classic. I've felt that's what John and I did. For John Cena and Roman Reigns, it was personal, and that's what you've got to have. 

"As long as we can peel back the curtain a bit and make people believe something may be going on a little bit more than what you see. Some things are said like, 'Whoa, was that a cheap shot?' To get them to that level is the most important thing."

Styles doesn't believe a five-star match isn't possible without the foundation of a juicy story to expand upon inside the ring. He also rejects the idea that Cena has ever used a major feud to step on and outshine his opponents. 

"The reason why people feel like guys get buried is because John Cena will take you and push you to another level and now it's your job to maintain that when you are done with John Cena," Styles said. 

Reigns ultimately agreed. Coming off such a physically demanding program with Braun Strowman, he has enjoyed the different experience of flexing his promo muscles and using the competition of working opposite Cena to help him grow. 

"It was nice to be able to change gears and get better at something," Reigns said. "I think I've definitely gotten better on the stick working with John. I have to give him credit for that. Like he said in one of his opening promos, you either step up or you step aside."

While Reigns is excited to see what he and Cena are able to produce on Sunday, one thing he isn't expecting is a rehash of his embarrassing "big dog" moment. 

"I'm doing a heavy duty zipper for No Mercy. Only one 'Big Dog' is coming out that night, and he's looking to fight and win," Reigns said. "I'm looking forward to it, but let's keep the zipper closed. No more malfunctions because that could've been quite embarrassing."