Mourinho was banished to the stand in south Wales after accepting two Football Association misconduct charges.
But United made light of their manager’s absence from the touchline as a blistering volley from Paul Pogba and Zlatan Ibrahimovic’s double gave them a comfortable 3-1 victory.
“I did what I do,” United manager Mourinho said when asked about having to sit in the stand.
“I made the changes, sent a message when something needs to be told to the team, and I was in the dressing room before the game and at half-time.
“One thing is the suspension that stops the manager to communicate, that is a problem.
“Another thing is the suspension when the manager can communicate with the team, see the team and speak to the assistants on the bench. So in this case it was not a problem.”
United were 3-0 up inside 33 minutes with Ibrahimovic ending his 10-hour wait for a Premier League goal.
The Swede had not scored in the league since the Manchester derby defeat on September 10.
But his goal drought ended on 609 minutes when he drove home low past Lukasz Fabianski and he then added another after being fed for the second time by the recalled Wayne Rooney.
“He is not a player who lacks confidence,” Mourinho said.
“I used to say that a striker that does not score goals and does nothing else is one player less.
“A striker that doesn’t score goals but does everything else is a very important player for the team.
“He was not scoring goals but he was doing everything else. He was working defensively, in the build-up, in the development of the second phase of attack, in the assists.
“He was contributing for the goalkeepers who play against us to be always the man of the match.
“So he was doing so many things I was not worried, but today we needed goals to win and he got it.”
Mourinho admitted he wants to change the culture at United. Before the game he revealed:
“Chris Smalling doesn’t feel he can play 100 per cent with his pain and Luke Shaw this morning told me he was not in condition to play.”
After the match, the Portuguese told Sky Sports:
“There is a difference between the brave, who want to be there at any cost, and the ones for whom a little pain can make a difference.
“Of course, it is not just the players, it is the players and the people that surround the players.”
However, Mourinho is confident of improving the situation, adding: “It takes time. But…it will not be an impossible mission.”
He added at his post-match press conference:
“We have players with problems, players on the pitch with problems.
“Every sport – and I know that because I have friends from other sports who play at the highest level – you play when you are not 100 per cent.
“I have a friend who is a big tennis player and he remembers more the times he plays in pain than without any pain.
“That’s what I mean, to compete you have to go to the limit. It is a cultural thing for some. But that’s not my culture. And more than me, Man United’s (culture).”