Manchester United escaped embarrassment from a lower league Blackburn, after coming from behind to win 2-1.
The championship club went ahead in the 17th minute after a fine finish from Graham, before Rashford equalised.
Then Ibrahimovic and Pogba came on to complete the comeback, with Pogba setting up Ibrahimovic to set up a quarterfinal fixture against Chelsea.
“I think the attitude of every player was really good,” Mourinho told BT Sport. “With a different attitude, we wouldn’t win. They gave us a really hard match and I am really happy with the players, of course.”
Mourinho went on to acknowledge the impact made by Ibrahimovic and Pogba, who were introduced just past the hour mark.
“I have important players on the bench and I can try to make them have an impact, but that doesn’t always work,” he said. “I spoke with Paul and Zlatan and they came with the right attitude.”
“We deserved to win, but Blackburn also deserve to go to Old Trafford,” he said. “But they can now focus on a very difficult Championship. A second match at Old Trafford would have been a disaster.
“I think the referees had everything under control and were really calm and even the ball boy to my right was really good.”