Otto Wallin believes Anthony Joshua is going through a "decline" and fancies his chances of dealing the Brit a fourth career defeat on Saturday.

Wallin will face Joshua in the main event of a stacked card billed as 'Day of Reckoning' in Riyadh, Saudi Arabia, after Deontay Wilder takes on Joseph Parker.

Joshua is reportedly close to agreeing to face Wilder twice in 2024, though a surprise defeat to Wallin would surely deal a fatal blow to those plans.

Joshua lost his IBF, WBA and WBO heavyweight belts to Oleksandr Usyk in 2021 before failing to recapture them in a rematch last year, though he has since responded with wins over Jermaine Franklin and Robert Helenius.

Though Wallin is still wary of the threat Joshua poses, the Swede senses an opportunity to add to his opponent's woes.

"I think that he's still one of the best fighters out there and he's done really well in his career and he deserves respect," Wallin told Stats Perform.

"Losing to Usyk and [Andy] Ruiz, there's no shame in that, they're very good fighters. But I think there's been a decline in his game, he hasn't really been the same lately. 

"But losing against those guys, anybody can. I think the timing of this fight is in my advantage. I have really good momentum and I don't know if he's in the same place."

Asked if he was confident of a surprise victory, Wallin said: "I am. I feel very good. I've done everything I can. 

"I remember my dad, he always used to tell me that once you step in the ring, you've got to know that you've done everything you possibly can to be as prepared as possible.

"I kept that with me over the years and I always try to prepare to the best of my ability. If I'm not ready now, I'm never going to be ready.

"I'm ready to go in there, have fun, I feel like I have no pressure. He has all the pressure and I can just go in and have fun and just beat him.

"We found out about this fight about seven weeks before December 23rd. We didn't have too much time. I think we had enough time because I was already in very good shape. 

"I had just had a win over [Murat] Gassiev on September 30th, I had a week off and then I was back training. I was in a really good place when we got the call so I was happy about that.

"Training has just been going really well. I think me already being in shape from the last fight and then also having the extra motivation for this fight made it all so much better and I feel like I'm in great shape, probably the best shape of my life."

Wallin has won his last six fights since losing to Tyson Fury via a unanimous decision in 2019, but the 33-year-old knows claiming the scalp of Joshua would be his biggest victory to date.

"It would be amazing. It's a big thing for me and a big thing for Sweden," he said.

"I get a lot of support over there. I think it would be amazing for me, my family, my team. So we are really excited about this opportunity."