Strikers could find it tough.
Drawing a blank at Blackburn on Saturday has sharpened the focus on United's injury-hit strike force - but they will barely have it any easier against the safety-first Blues.
Alex McLeish's Wembley-bound side were struggling at the turn of the year but a return to the defensive basics has seen them move away from trouble at the foot of the Premier League.
A pair of clean sheets in successive 1-0 victories has helped the Blues to within two points of Newcastle.
And Pardew knows that his United side will have to bear their teeth to come away with anything from the second city. "I just think Birmingham are a side that restrict you in terms of attacking them," the manager said.
"They're very solid, they don't allow you to have a lot of room between the lines so it's difficult to score in open play.
"You can boss the game, like we did at Blackburn, and hopefully create chances through set plays and the odd time when you manage to pull them around.
"But they're a disciplined side, a hardworking side and they have some very, very good players.
It's a very important game I feel and we'd like to get three points on the board. It's not an easy thing to do there - I think they've only lost two at home all year, so they've got a very, very good record."
Birmingham's recent improvement has coincided with the return of pounds 6million striker Nikola Zigic - at 6ft 8in the tallest player in the Premier League - to the firing line.
He has hit winners in both of Birmingham's recent victories, but Pardew reckons Mike Williamson can match the rangey striker.
"He's a funny player - he can look awkward at times and uncomfortable at the level, if I'm honest," Pardew said.
"Then you get the right delivery into the box and he's very difficult to defend, a little like Andy Carroll, of course. If that delivery's right they're difficult.
"In (Mike) Williamson we've got a player who can deal with a big player like he did with (Chris) Samba at Blackburn. I thought he was excellent. Samba only got one header in, so we're hoping for the same job from Williamson."
TOUGH AWAY DAY Alan Pardew