Rooney picked up an ankle knock in the win at West Brom last weekend, leaving the pitch before hobbling back on for the closing moments of the 2-1 victory. Meanwhile Van der Sar has missed United's last two matches with Tomasz Kuszczak deputising for the Dutch keeper.
In last season's competition, United were knocked out in the third round by Leeds United and Ferguson, who confirmed Rio Ferdinand is fine after being rested for Tuesday's clash against Stoke, is planning to field a stronger team to avoid a similar fate.
"We're hoping that Edwin and Wayne are fit for Sunday, I think it's important for the reasons of Wayne's form, he's been fantastic, we're really pleased with the way he's performing. And Edwin's experience, there's no definite indication they're going to be fit but they have a chance. Other than that it will be the same squad we've been operating with," he said.
"The FA Cup's the FA Cup. It's a tournament you can never be sure about. We made a mistake last year, we picked a team which we thought would be good enough to beat Leeds (then a League One side) but we got a reminder that the FA Cup is a Cup which has shocks, we got one last year and hopefully we don't get one this year. I think I picked the wrong team last year."
Meanwhile, Ferguson has reacted coyly to questions over the future of Michael Owen, who is out of contract at the end of the season and has been linked with a departure.
"Now he is back fit, Michael will always be considered part of the squad and he will play in some big games,'' Ferguson told Key103. "I have not spoken to him about next season. There is no need for me to discuss that at the moment.
"He is a terrific player and a role model in the dressing room. He has never missed a session while he has been fit.''