Goals from Romelu Lukaku and Nemanja Matic were enough to seal a 2-0 victory for United against Brighton & Hove Albion at Old Trafford, ensuring that United's only remaining hope of silverware is still alive following their Champions League exit in midweek.
However, Mourinho was unhappy with his side's performance and questioned the quality, personality and desire of a number of his players.
"The performance was not as good as the result, the result was better than the performance. We deserved to win clearly, we had the match under control but we didn't play well. We didn't play as I wanted them to play, we didn't play as I prepared the team to play," he told BBC Sport.
"Sometimes there is a contradiction between what you work on in the past two days and what you did on the pitch. That is more frustrating than the result. Once more I wasn't happy with the connection in the build up. I blame everybody. I blame the defenders in possession because they always made the easy decision to play square passes, not looking forward, vertical or between the lines. I blame the attackers because their movement for that connection, they were too scared to do it.
"Not many players had the personality to play under the pressure of one knockout at home. The attitude was not bad but the point is the lack of personality. Matic was an island of personality, the one who clearly wanted the ball, made mistakes, but wanted the ball, wanted to play.
"He was an island of class and personality to play for Man Utd, surrounded by people who need more, especially in moments like this. When the sun is shining it is easy to play football. When you win matches everything goes in your direction. When it is dark, and you're under pressure, only the top ones can do it. Today we didn't have many top ones."
United enjoyed 61% of the possession at Old Trafford but managed only two shots on target - four fewer than Brighton.