The 35-year-old scored his 17th league goal of the season to break the deadlock at the Stadium of Light.
Up until that point, United had struggled to carve clear cut opportunities.
And Mourinho praised Ibrahimovic for his ability to break teams down.
Manchester United player ratings against Sunderland
Sun, April 9, 2017
Express Sport rates how the Manchester United players performed during their Premier League clash with Sunderland
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Which Manchester United players impressed during their clash with Sunderland?
Manchester United manager Jose Mourinho
He said: "It was open at 0-0. We were in control without danger. We were playing quite compact and solid.
"You need these players to break it. Every team has a couple of them.
"Zlatan did that. We felt the game was in our pocket. In this beautiful weather the game was played at a more slow intensity."
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