World Extreme Cagefighting McCullough began his
mixed martial arts career with a first-round
TKO victory at the Palace Casino in
Lemoore, California, in 2001. Between 2003 and 2007, "Razor Rob" went 10-1 with nine stoppage victories and only a split-decision loss to Harris Sarmiento, which he later avenged. McCullough defeated Muay Thai fighter
Kit Cope at
WEC 25 to win the vacant
WEC Lightweight Championship. He defended the title once by defeating
Richard Crunkilton by first-round TKO. On February 13, 2008, he lost his title to
Jamie Varner when Varner defeated him by
TKO due to strikes in the third round. After losing his title, McCullough struggled over his next four fights in the now-defunct
WEC. He defeated Kenneth Alexander by split decision but then lost to
Donald Cerrone. but he fractured his right hand and received minor damage to his ankle and subsequently underwent surgery to repair his hand. McCullough was expected to return to the cage against
Anthony Pettis on November 18, 2009, at
WEC 44; but Pettis had to pull out of the bout with an undisclosed injury. McCullough instead faced WEC newcomer
Karen Darabedyan. McCullough lost to Darabedyan via split decision. With three losses in his last five fights, McCullough released by the WEC and would eventually join
Tachi Palace Fights, returning to the venue where his career began, and had somewhat of a resurgence. McCullough defeated Isaac de Jesus by first-round
TKO on July 9, 2010, at Tachi Palace Fight 5. He then defeated
UFC veteran
Corey Hill by unanimous decision on September 9, 2010, at Tachi Palace Fight 6.
Bellator MMA On October 14, 2010, McCullough signed with
Bellator to compete in the promotion's upcoming Season Four Lightweight Tournament. He was knocked out by a counter right by
Patricky "The Pitbull" Freire.
DREAM McCullough next faced
Shinya Aoki at
DREAM 17. He lost the fight via submission in the first round. ==Personal life==