A fourth middleweight bout has been added to the second UFC pay-per-view set for January, as Tim Boetsch meets Thales Leites at UFC 183.

Set for January 31 from Las Vegas, the event features the return of former UFC champion Anderson Silva against ex-Strikeforce titleholder Nick Diaz.

Boetsch (18-7) owns a 9-6 Octagon mark overall, including wins over C.B. Dollaway and Brad Tavares as part of a 2-1 run. He has also fought – and lost – to the likes of Luke Rockhold and Mark Munoz.

“The Barbarian” is 6-3 in his last nine overall, a stretch that features victories over Yushin Okami and Hector Lombard.

Leites (24-4) has won nine of 12 over two stints with the promotion. The former No. 1 contender returned in 2013 and has won four in a row, stretching his current win streak to seven straight.

In 2009, Leites worked his way into the role of title-contender, where he lost to Silva via decision. A second straight defeat later that year led to his release from the UFC.

Below is the current lineup:

Middleweight: Anderson Silva vs. Nick Diaz

Welterweight: Thiago Alves vs. Jordan Mein

Middleweight: Andy Enz vs. Thiago Santos

Middleweight: Ildemar Alcantara vs. Richardson Moreira

Middleweight: Thales Leites vs. Tim Boetsch