Muhammed Lawal will face BAMMA combatant Brett McDermott Dec. 29 in RIZIN Fighting Federation's inaugural heavyweight grand prix.

The news comes after the withdrawal of Lawal's original opponent, Mark Godbeer, due to injury.

The Englishman McDermott comes into his bout opposite King Mo with a 5-2 record (four knockouts), going 2-1 in his last three under the BAMMA banner. McDermott first made a name for himself in the world of sports as a professional rugby league footballer, most notably representing England's Barrow Raiders.

He retired from the sport in 2011 after testing positive for anabolic steroids.

King Mo (16-4, one no-contest), meanwhile, has won four straight, last defeating Linton Vassel at Bellator 142: Dynamite 1 Sept. 19. While the 34-year-old fighter contested the majority of his career at light heavyweight, he does have prior experience north of 205 pounds, most recently besting former UFC heavyweight Cheick Kongo via split decision at Bellator 134.

In a press release, RIZIN FF also officially announced a matchup between Bob Sapp and sumo wrestling legend Akebono Taro for their Dec. 31 event. The bout, which will be contested under Shoot Boxing rules, serves as a rematch to their 2003 tilt, which Sapp won via first-round knockout. That fight, unlike the rematch, was fought under kickboxing rules.

Shoot Boxing rules allow for kicks, punches, knees, elbows, throws and standing submissions, while common fouls – such as groin strikes, bites, headbutts and shots to the back of the head – are still disallowed.

"It has been a while since I last fought on [New Year's Eve], and [I'm] very excited," Sapp said in the release. "And to be facing my nemesis once again. Last time we fought, we made history, and that was a great honor. I would like to aim for making history again, and I assure you it will be an exciting fight."

"I have been living with grief and defeat for the past 12 years," Akebono added. "I have carried a thought of redemption deep inside and got the offer at the perfect timing. I never want to have to feel that way again, so I want everybody to come watch the new Akebono. I’m going in there for the win."

In other RIZIN FF notes, it was announced that Hiroya Kawabe will square off against Akiyo "Wicky" Nishiura on Dec. 29, and Takeru Segawa will take on Chinese Muay Thai champion Yang Ming on Dec. 31. These bouts will be contested under K-1 rules.

"The new K-1 has become popular in such a rapid rate, and I am happy that they are going to be sending their top, young talent to our ring," said RIZIN FF Chairman Nobuyuki Sakakibara. "We would like to match both K-1 representatives up with tough opponents."

Sakakibara also noted that Nam Jin Jo suffered a knee injury during training and was forced to withdraw from his Dec. 29 matchup against Yuki Motoya. Shoot Boxe Academy's Felipe Efrain will replace him in that bout.