Anthony Joshua can proudly call himself the ruler of the heavyweight division.

He owns two titles, he’s undefeated, and most importantly, he’s a bona fide mega star in the U.K.

Joshua is set to fight in Wales again, and he’ll do so Saturday before a sold-out crowd of 78,000 against late-replacement Carlos Takam (5 p.m. ET, Showtime).

The Frenchman stepped in when Kubrat Pulev was forced to withdraw with a shoulder injury.

No matter, Joshua (19-0, 19 knockouts) is ready for the challenge. He knows he can’t live off his breakthrough victory over Wladimir Klitschko forever. Sure, it was about as big as boxing victories get: a KO of a legend in a legit heavyweight classic. But that’s in the past, and if Joshua’s star is going to continue to shine, he’ll have to keep knocking guys out.

“We’re going to have to put that Klitschko win to the side at some stage because boxing is unforgiving,” Joshua said. “That was that. This is now. Carlos is a completely different animal than Klitschko.

“Who knows what’s going to happen in that ring Saturday. This division is unpredictable. You saw I got tired in the fifth round against Klitschko. Am I going to find out I’m only a five-round fighter? Takam is tough and can go the distance. He’s definitely going to take me into late waters and that’s where it’s going to be interesting.”

Is Joshua, 28, simply an incredibly thoughtful and honest fighter, or is he trying to sell the fight? Perhaps a bit of both, but it’s still surprising to hear the heavyweight champ admit he might possess major stamina issues.

He’ll look to clean those up against Takam, a solid fighter who is 0-2-1 in his three notable bouts: a knockout loss to Alexander Povetkin, a draw with Mike Perez in his lone HBO outing and, most recently, a decision defeat to Joseph Parker.

Takam (35-3-1, 27 KOs), at 36, does own a wealth of experience after representing Cameroon in the 2004 Olympic Games. He’s highly unlikely to give Joshua any problems, but he could be the kind of opponent to help Joshua build his game. Naturally, Takam has other idea.

“My experience will help me win the fight,” Takam said. “I’ve been in there with a champion. When we get in the ring it’s just two fighters. Only at the end of the fight will we know who the real world champion is.

“I saw Joshua go down. I saw he has a weak point, and we’ve been working on targeting that.”

Promoter Eddie Hearn actually had Takam on standby, training, in the event a replacement was necessary.

“We’re going to have to put that Klitschko win to the side at some stage because boxing is unforgiving,” Joshua said on Thursday. “That was that. This is now. Carlos is a completely different animal than Klitschko.

“Who knows what’s going to happen in that ring Saturday. This division is unpredictable. You saw I got tired in the fifth round against Klitschko. Am I going to find out I’m only a five round fighter? Takam is tough and can go the distance. He’s definitely going to take me into late waters and that’s where it’s going to be interesting.”

Takam (35-3-1, 27 KOs) has experience in close bouts with reigning WBO Heavyweight Champion Joseph Parker and former challenger Alexander Povetkin. The 2004 Olympian from Cameroon enters the contest having boxed more than three times the professional rounds as Joshua.

“My experience will help me win the fight,” Takam said. “I’ve been in there with a champion. When we get in the ring it’s just two fighters. Only at the end of the fight will we know who the real world champion is.

“I saw Joshua go down. I saw he has a weak point, and we’ve been working on targeting that.”

Promoter Eddie Hearn actually enlisted Takam on standby in the event a replacement was needed, so the fighter figures to be in good shape. He weighed in at 235 1/2 pounds Friday and looked trim and ready. Joshua, as always, appeared to be in incredible shape, but he has just one regret.

“With [Takam’s] style and his strength, I wish I came into this fight heavier so we could just stand there and slug it out with each other,” said Joshua, who still weighed a career-high 254 pounds. “Why’d I come in lighter? I thought I was fighting Pulev – a real amateur-style boxer.

“I had to stay off the line, jab with him and match his speed. Takam is a completely different style of fighter so I might have come in a bit heavier if I knew I was fighting Takam.”

It doesn’t figure to matter. Joshua displayed impressive maturity against Klitschko, and even some deft defensive movements. There isn’t anything Takam can do that Joshua didn’t see against Klitschko in April.

And with a win Saturday, Joshua’s IBF mandatory will be fulfilled, and he can look forward to some truly major fights in 2018.

Mike Coppinger is the Senior Writer for RingTV.com. Follow him on Twitter: @MikeCoppinger