"I've actually spoken to him three times now. I called him after the first day of rehearsal and I was like, 'Oh, boy. What did I get myself into?'" McLean tells ET's Lauren Zima a week before the new season premieres. "He kind of freaked me out the first time we spoke because, granted, he was going based on his experience and this is different for everybody, obviously. But he said, 'Dude, just enjoy the moment. Enjoy the process.' He's like, 'I wish I would've done a couple things differently.' He listed all these things and he's like, 'Dude, just go have fun. If anyone can do this, you can do it.'"
McLean has been dancing since he was a kid, auditioning for BSB when he was only 14. But while he's used to the boy band's signature dance moves, he's still learning a lot about other genres of dance.
"I'm feeling great. I've definitely been sore, I'm not gonna lie, in places I didn't know I had on my body. But again, I'm literally doing something that I've never done before," McLean admits. "Having to reprogram my brain from 30 years of dancing more urban-style dancing to having really good lines, putting my chest up and my head up, or back. That's the thing that I'm learning about ballroom, that your head is back, like someone's pulling you from behind."
While fans don't know who his partner is, the singer says that they have been "grinding" and putting all the work in for their first dance together. Their first performance is to a song by The Weeknd, and McLean says "it is fast."
"I finally can, honest to god, say I am feeling really good. My partner and I have been grinding it out," he shares. "It was pretty easy to learn the steps, but to do it right, that's another conversation. Now it's a matter of, I gotta breathe, I gotta have fun with it. I don't need to look like a deer in the headlights, that's not what America wants to see."
As for the possibility of viewers seeing McLean pull out any of his Backstreet dance moves, the "Quit Playing Games (With My Heart)" crooner says, "That would be cool."
"If we end up doing a Backstreet Boys song down the road, I think it would be cool to add some kind of element from what the fans know," he teases. "Because the fans know a lot. If it's the hat routine, that's a pretty signature Backstreet move."
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AJ McLean Talks His Quarantine Fitness Habits & Girl Dad Duties (Exclusive)
Meanwhile, McLean's advice from Carter, as well as his dancing history, may work to his advantage, but he's still worried about a couple of other contestants. While many celebs contestants this season look to Johnny Weir as their biggest competition, the former Olympic figure skater looked to McLean.
And while Weir revealed that he was an *NSYNC fan back in the day, McLean replies, "It's OK, so was my wife."
"She liked their dancing better, but she likes our songs better. So I'm like, 'Really?' and I still married her," he cracks. "When she was 17, she was the designated driver for her younger friends and she drove to see us in Vegas. She was in the nosebleeds sections during the Black and Blue tour, and I totally asked her after we got engaged, 'Did you ever think, that day, looking down at those guys, that you'd ever marry one of them? She's like, 'No, and least of all you.'"
McLean, however, also sees Weir as competition. "I just met Johnny in the parking lot. We were talking car to car, at least 20 feet apart. I'm a big fan of him, nicest man on the freaking planet," McLean marvels. "And if I were to say any specific one of us that I am a little concerned about it is definitely Johnny. Even he was telling me, 'My hips don't move that way. I'm on the ice and it's totally different.'"
"Here's the thing about this show, you never know. There's people who have zero dance experience and go all the way," McLean adds. "The season that [Nick] came in second and Bindi Irwin won, she doesn't have any dance experience. It's about the process."
McLean is also competing against fellow musician Nelly. The two have crossed paths during their careers and previously toured together. And while Nelly told ET that McLean is the one he's looking out for, the boy bander says you might have to watch out for the rapper.
"Nelly, he's nervous, but he's going to be great. The guy's got rhythm. He can move," McLean expresses. "We toured together two summers ago, yeah, he's going to do just fine."
As he gears up for his big DWTS debut, how do the show's costumes stack up to the BSB tour looks?
"I've already seen the designs for opening night and its not too far off," he says. "Obviously things are more formal, but I talked to my partner last night about future dances. If I make it that far, based on the certain songs, I'm like, 'Hey, can I cut the sleeves off my jacket?' I think I'm the most tattooed celeb that's ever done this show. That's a big part of me, so let's show it."
And as far as going shirtless for the show?
"If they ask me, I'll do it," McLean, who has been working on his fitness and getting in shape, says. "I'll tell you what, I feel more confident doing it now than nine months ago."
The all-new season of Dancing With the Stars premieres Monday, Sept. 14 at 8 p.m. ET/PT on ABC. In the meantime, tune into Entertainment Tonight on Thursday for more with McLean.