Carwin, Kawajiri officially sign with Rizin FF

Former interim UFC heavyweight champion Shane Carwin is coming back in a big way.

After teasing his signing with Rizin FF earlier this week, Carwin was confirmed for the Japanese promotion's upcoming openweight Grand Prix tournament during a press conference Thursday.

The 41-year-old Carwin hasn't fought since June 2011, and he retired in 2013 citing numerous injuries that rendered him unable to compete. In September of this year, Carwin announced he was free from his UFC contract and would be attempting a comeback.

One possibility Carwin mentioned was a meeting with heavyweight legend Fedor Emelianenko, but it appears he'll instead be entered into the Rizin Grand Prix in December as a wild-card participant with a bye into the second round.

Carwin is best known for his six-fight stint with the UFC from 2008-2011 that saw him knock out four opponents in the first round. That run was capped off by a win over Frank Mir that earned Carwin an interim UFC belt. Carwin would attempt to unify the titles in his next fight against Brock Lesnar, staggering the champ before succumbing to a submission in the second round.

Carwin's debut is expected to take place Dec. 29 at Rizin FF 3 in Saitama, Japan.

Also announced was the official signing of Japanese star Tatsuya Kawajiri. Kawajiri could potentially debut at either the Dec. 29 or Dec. 31 shows, reports MMA Fighting's Ariel Helwani.

Kawajiri most recently fought in the UFC, going 3-3 with a notable win over Dennis Siver. He faltered against top-10 competitors Dennis Bermudez and Cub Swanson before asking the UFC for his release in October.

Prior to competing inside the Octagon, "Crusher" was a feared competitor at 145 and 155 pounds in Japan. Kawajiri's professional MMA record stands at 35-10-2.

- With h/t to Bloody Elbow