Redknapp to ring changes in Cup
The game is a rematch of last season's final which Spurs lost on penalties.
"We've players who need matches - the likes of Alan Hutton, Gareth Bale, Jermaine Jenas and Robbie Keane - so we'll change a few around and freshen things up a bit," Redknapp told reporters on Monday.
"The good thing is we've plenty of options."
Ireland captain Keane will make his first start for Tottenham since his country were controversially eliminated in the World Cup qualifiers after Thierry Henry handled the ball in the lead up to France's equaliser in their playoff.
The striker was an unused substitute for Tottenham's 9-1 Premier League victory over Wigan Athletic at White Hart Lane on Nov. 22 and came on as a late replacement in the 1-1 draw at Aston Villa on Saturday
Jonathan Woodgate, who missed the Villa match, is again ruled out with a groin problem while Ledley King is still recovering from a hamstring injury sustained against Sunderland on Nov. 7 so Michael Dawson and Sebastien Bassong will continue in central defence.
United manager Alex Ferguson said he would again field a young side despite criticism of their performance against Besiktas last week when a 1-0 defeat ended the club's 23-game unbeaten home run in the Champions League.
"It will be the same players that played on Wednesday," Ferguson said on the United website. "Their future is well marked out, I think."