Mourinho opted to start the game without a recognised striker and the Portuguese boss feels that it makes his side more mobile in attacking areas.
"I go for mobility," Mourinho told Sky Sports News. "I want to try to win the game and instead of one target man we play with four attacking players and cause them problems.
"I am not afraid to make decisions and in the end they will say: 'Jose was right' or 'Jose was wrong'. We have played well with this system in training and we were happy with the gameplan."
Mourinho also revealed that he was not surprised by the inclusion of Wayne Rooney in the United XI despite the interest from the Blues.
"I was not surprised, he is a fantastic player," added the Blues boss.
"They have him, so why not play him if he is ready. I prepared for the game with him in their team and without him, we're ready."
You can catch live commentary of tonight's game here.