Mourinho has praised his side for their organisation throughout the game, while admitting that the Blues had the better start to the contest.
"We beat a fantastic team, for some reason they were the champions last season, and for some reason they played well against Barcelona, and for some reason they started the game very well," the manager told Sky Sports News.
"So, we beat a very good team, we had to be organised, everybody had to follow the game plan and have spirit. We beat a very good team. They started very well and when they hit the post, I was looking at my players, what can we do, who can I blame, but it was such a lovely move, we couldn't stop it.
"But we found a way to play against them, and we had a good control of Eden Hazard. Willian is an amazing player and he killed us with the goal. But we had more control of the game than them, without creating lots of chances."
The result leaves Chelsea six points behind United in the Premier League table.