The following is an note from UFC.com's main page:
Leg Infection Forces Sadollah from UFC 91 Card
By Thomas Gerbasi
A leg infection has forced The Ultimate Fighter season seven winner Amir Sadollah to withdraw from his UFC 91 bout against Nick Catone this Saturday. After an exhaustive search for a replacement, the middleweight matchup will not be replaced on the card, but the welterweight showdown between rising stars Dustin Hazelett and Tamdan McCrory will be bounced to the pay-per-view portion of Saturday’s event.