Midfielder ready for match against in-form sides.
"But, for now, we've got to concentrate on the league. Oldham and Blackpool dropped points at the weekend, so we need to use our result against Charlton to give us some momentum into the two home games."
He added: "We've played Spurs in pre-season, but a cup match against a top flight side will be completely different.
There is an element of familiarity with a recent pre-season match against the London side, but Alex knows that the match at the end of January will be a very different proposition, whichever side progresses through the Third Round replay.
"Spurs have been one of the best sides in the Premier League this season and Leicester have been the surprise package, so it will be a good game whoever we get."
"It's a great one for the fans that have stuck with us this season and everyone will be looking forward to it.
And, whilst keeping his attentions firmly on the three league matches between now and then, he told the official website: "Of course, everyone is very happy.
The U's will discover next week their next opponents, with Leicester and Tottenham going head to head whilst the U's take on Fleetwood in League One.
Colchester United midfielder Alex Gilbey can't wait to get stuck into the U's Fourth Round tie in the Emirates FA Cup.