Chelsea defender David Luiz says Jose Mourinho "tried everything" to improve Manchester United before his sacking.
Monday's fixture is a repeat of last season's FA Cup final, which Chelsea won 1-0, and a third consecutive meeting between the teams in the competition. Luiz spoke about United's form under Ole Gunnar Solskjaer.
"Even before they were a great team with a great manager, Jose Mourinho tried to do everything for the best for Man United but then they decided to change," said the Brazilian.
"It became Solskjaer and he's doing amazing because he's a great coach and also he has great players. United have had the same team for a long time, they understand his philosophy and they try to enjoy it."