Although the competition may not be viewed by some as a priority for the Reds, the club have enjoyed an excellent record in recent years and it enables the boss to hand game-time to fringe members of his squad and promising youngsters.
With another huge Barclays Premier League encounter to come in an early kick-off on Saturday, against an Arsenal side buoyed by the remarkable 7-5 win at Reading, there will be changes but the manager is clear on his objective.
"Obviously, we'll make changes for Wednesday," he informed MUTV. "The squad that played against Newcastle will be in place again. I think I will make some changes there but not a lot as we don't want to lose down there anyway. We want to continue in the Cup but there will still be some changes."
The fourth round tie looks like coming too soon for defenders Chris Smalling and Phil Jones.
"Chris has been doing training with us back on the football side of it and we'll try and push him on quickly," added Sir Alex. "But I don't think he'll make the midweek game at Chelsea, although I'm sure he'll be ready for the following week.
"Phil Jones maybe needs another week on the physical part before he can train with us but the good news is he's not far away."