if Coventry City or Sheffield United were to be involved in an FA Cup Second Round Replay, then it might not be played until the week before Christmas.
The date for any Second Round replays is currently Tuesday December 13th or Wednesday December 14th depending on the demands of television.
However, with the Sky Blues due to face Sheffield United on Thursday December 15th in a game which has been brought forward by Sky TV from December 17th, neither City, if they draw at Cambridge or Sheffield United, if they draw at Bolton, is particularly going to want to play two matches in three days and Sky are probably going to kick up a fuss if the match is moved back to its original date as the City v Sheffield United match is part of its ten games in ten days series.
So it is possible that if either City or Sheffield United need a replay in their FA Cup Second Round games, any replay will take place in the week commencing December 19th.