Bader (8-0), a two-time wrestling All-American at Arizon State University, compiled a 7-0 record in various promotions before capturing The Ultimate Fighter 8 light heavyweight title with a first-round knockout of Vinicius Magalhaes. Marrero (10-2) is a three-fight UFC veteran, defeating Cheick Kongo in his promotional debut in late-2006 before dropping back-to-back fights to Gabriel Gonzaga and Wilson Gouveia that temporarily forced him out of the UFC. Marrero earned his return trip to the octagon by going 4-0 since his departure, most-recently defeating Steve Steinbeiss via split decision at a November WEC event.
An up-and-coming middleweight, Simpson (4-0) debuted in the WEC in November with an 18-second knockout of David Avellan and will now debut in the UFC after the WEC cut the 185-pound division at the end of 2008. McKenzie (12-5) is also a WEC veteran, having fought on and off in the promotion since 2003, most-recently earning a third-round submission of Jeremy Lang last June.
Efrain Escudero vs. Jeremy Stephens, Junie Browning vs. Cole Miller, and Ricardo Almeida vs. Matt Horwich are also slated to take place at UFC Fight Night 18.