Just 14 senior outfield players remain for selection, meaning there is unlikely to be any repeat of last year's sweeping changes, which led to an early exit at the Reebok against Sheffield United.
"I haven't got any choice, I can't chop and change," Megson said.
"We brought Nicky back from Birmingham because he wouldn't have been eligible for the FA Cup anyway, but we needed the numbers.
"Last year, we couldn't have afforded to take the FA Cup in our stride because of the circumstances we were in.
"But aside from the one change I'll have to make because of Gavin's suspension, there isn't a lot more I can do about it."