John Sutton's double ended a three-month unbeaten run for Celtic and secured Motherwell's first win over the Hoops for almost three years.
But Motherwell have not competed in a Scottish Cup semi-final since their 4-3 defeat by Rangers in 2003 and McCall is desperate to lead them back to Hampden in the 20th anniversary year of their epic final triumph over United.
"It's a huge match," the former Rangers and Scotland midfielder said.
"If we were to win on Sunday and get to the semi-final then it would be bigger than beating Celtic for me. What it means to the club and the fans to get to another semi-final is fantastic.
"We know it's a tough job. Apart from the Old Firm it is probably the most difficult tie we could have been given. Away at Tannadice - especially with them getting their players back and having three successes - is a hard game.
"But I believe if we can perform like we have done in some games this season and are at our best, then I think it could be a great cup tie. When we've played well we've played very well and we'll need one of those performances to get through on Sunday - but we're capable of it."
Source: PA
