Derek Brunson Replaces Injured Karlos Vemola, Meets Chris Leben at UFC 155

The event takes place Dec. 29 at MGM Grand Garden Arena in Las Vegas and is headlined by a heavyweight title rematch between reigning champion Junior dos Santos against former kingpin Cain Velasquez. Verbal agreements are in place for the Brunson-Leben showdown, according to the announcement.

Brunson, 28, began his career a perfect 9-0 before stumbling in his two most recent outings, first dropping a split decision to “Ultimate Fighter” Season 3 winner Kendall Grove before being knocked out in just 41 seconds by former Strikeforce champion Ronaldo Souza this past August. A representative of Jackson’s MMA, Brunson earned four victories last year, three of which came under the Strikeforce banner.

An alumnus of the original “TUF” series, Leben is known for his knockout power and ability to absorb punishment. Though the 32-year-old posted a trio of wins in 2010, he has lost two of his last three fights, most recently suffering a second-round technical knockout to Mark Munoz in November 2011. “The Crippler” tested positive for painkillers following that defeat, prompting the UFC to suspend the fighter for one year.

Vemola, 27, suffered a fractured cheekbone in training that caused his withdrawal. The Czech’s clash with Leben would have marked his third as a UFC middleweight and his fifth appearance overall in the Octagon. Vemola, who debuted in the UFC has heavyweight, holds a 2-3 promotional record, recording wins over Seth Petruzelli and Mike Massenzio in his two-plus years with the organization.