NFL great Frank Gore is taking on a new sport: boxing.

The former San Francisco 49ers star running back has spent the last few months training to get into the ring, according to the NFL Network. And he is set to fight former basketball star Deron Williams on Dec. 18 as the undercard match for the Jake Paul-Tommy Fury fight in Tampa, Showtime Sports announced on Tuesday.

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Xander Zayas (L) and Frank Gore (R) walking to the ring before Xanders fight against Dan Karpency at State Farm Arena on October 23, 2021 in Atlanta, Georgia. 

Xander Zayas (L) and Frank Gore (R) walking to the ring before Xanders fight against Dan Karpency at State Farm Arena on October 23, 2021 in Atlanta, Georgia.  (Photo by Mikey Williams/Top Rank Inc via Getty Images)

The fight will last four rounds, and it has a contracted weight limit of 215 pounds.

"I've been training for both — football and boxing," Gore told NFL.com back in September. "I've always loved boxing, so that's what I've been doing. And we're trying to make a fight happen. If we do that, you'll see me in the ring."

Gore, 38, is a five-time Pro Bowler and is the NFL's third-leading rusher of all time. Not only did he spend time with the 49ers, but Gore also played for the Indianapolis Colts, Miami Dolphins, Buffalo Bills and New York Jets.

Professional basketball player Deron Williams is seen in attendance during the UFC 228 event at American Airlines Center on September 8, 2018 in Dallas, Texas. 

Professional basketball player Deron Williams is seen in attendance during the UFC 228 event at American Airlines Center on September 8, 2018 in Dallas, Texas.  (Photo by Josh Hedges/Zuffa LLC/Zuffa LLC via Getty Images)

Gore reportedly received interest from NFL teams this season, but he wanted to focus on a potential boxing career.

"I’m excited to be fighting on this card and can’t wait to show the world what I’ve been working on," Gore said in a statement. "Boxing has me excited, and on Dec. 18 expect fireworks!"

Williams, on the other hand, was a three-time All-Star with the Utah Jazz and Brooklyn Nets. He also was a two-time Olympic gold medalist before retiring from the NBA following the 2016-17 season.

NFL running back Frank Gore of the Buffalo Bills speaks onstage during day 2 of SiriusXM at Super Bowl LIV on January 30, 2020 in Miami, Florida.

NFL running back Frank Gore of the Buffalo Bills speaks onstage during day 2 of SiriusXM at Super Bowl LIV on January 30, 2020 in Miami, Florida. (Photo by Cindy Ord/Getty Images for SiriusXM)

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"Combat sports have been a part of my life since my youngest days," Williams said. "Before I was a basketball player, I was a wrestler. Since 2015, I have had the privilege of owning an MMA gym, and through that, I have trained in various martial arts to stay active. Over the last year, I’ve been waiting for the right opportunity to translate my training into a professional debut."