The main reason for the delay would be to create some space between the start of The Contender and the completion of Fox's quickie ripoff, The Next Great Champ, which has bombed in the ratings. NBC would prefer to have its show viewed as the original that it is, not as a variation of a disappointing flop.
In addition, since Champ will not complete its run until the end of November now that Fox has sent the show on a two-week hiatus, NBC would be able to launch a marketing campaign for The Contender that does not run the risk of confusing viewers about the two shows. Perhaps the NBC executives are worried that Fox might burn its remaining Champ episodes in a deliberate attempt to confuse potential The Contender viewers, under the theory that, if Fox couldn't have the hit with a boxing-reality show, then NBC shouldn't be able to have it, either.
A January start would also enable The Contender to verify its appeal to young women, who have proven to be a key market for Mark Burnett's successful reality-competition efforts ... but who have largely avoided tuning in to The Next Great Champ.
One problem with this strategy, though, is that NBC may not have a replacement reality program (such as Average Joe 4 or the diet show The Biggest Loser) ready for a November launch. Then again, considering that The Contender cost NBC a record $2 million per episode, even a schedule hole might be preferable if it gives The Contender the best shot at a Nielsen title.