"It is a big game and we have got to get ourselves right," he says. "The carrot is there with the reward being another home game. No disrespect to Preston but you should have a good chance of winning a home game against a side a division lower.
"I think it is vital to win as it would be a great boost for everybody involved at West Ham."
Christian is confident that the team can still function without Paolo Di Canio, suspended for three games, and Michael Carrick, injured for six weeks.
"We have got to get on without Paolo and Michael but Steve Lomas has come in for a while and Jermain Defoe has been fantastic when he has played, so we have got cover there - and goals as well.
"Jermain is up there with the top scorers at the club and for the number of games he has started that is some strike record.
"Maybe he is not yet a 40 games a season player - but three or four back to back will be no problem for him.
"We have got Paul Kitson as well so the optimism is there, certainly."
Also in the back of his mind, though, is the poor away form, and, with a trip to Bolton looming at the weekend, he explains: "It is just a mentality and a discipline thing. We have probably got to work that extra 10% harder and it is a case of getting that inside everyone's head as a team and working really, really hard when we don't have the ball."
Christian feels the win against his former club Blackburn on Saturday augurs well for the cup tie, as both the attacking and defending was satisfying, and he adds: "Blackburn were always dangerous as they have a lot of pace in the team, but at times we were cutting through them.
"Trevor made a bit of a difference coming back and with Fredi's pace the penetration was there which sometimes we don't have away."