Chicharito became a more regular player than Dimitar was.
"Some people like to see players run through brick walls all the time. Dimitar is not that type of player, but he is a very talented player and he had a decent goalscoring record here, you must remember that."
As for the chance to reach the fifth round of a competition United have not won since 2004, Sir Alex is determined to get his hands on the trophy again.
"I think we all know that we haven't done as well in the FA Cup for a few years now," he added. "It's a cup which has fantastic appeal given our record in it. We have benefit of the home draw, which I always say we'll take that any time. It's going to be a challenge for us. But we would take playing anyone at home."