United defeated Leicester City 2-1 to lift The FA Community Shield supported by McDonald’s at Wembley, after Jesse Lingard and Zlatan Ibrahimovic found the net to counter Jamie Vardy’s effort.
Leicester City 1-2 Man Utd
FA Community Shield supported by McDonald's
Wembley Stadium connected by EE
Sunday 7 August 2016
And Mourinho told BT Sport: "The first half performance was much better than the second. The team isn't fit enough yet.
"When Leicester increased the pace, they had three quick players and changed the game.
"It’s an important victory but we have lots of work to do.
"I would be not ambitious if I said it was a fantastic performance. It wasn't. It's always important to start with a trophy."
Mourinho was equally restrained in his praise for Ibrahimovic, who despite his winner, had a quiet game in attack for the Emirates FA Cup holders.
The Portuguese said: "Zlatan will be more dangerous when we are more dominant and play closer to the box. He's not a fast player like Jamie Vardy, who can play 50 yards from the box.
"He needs the team to play and produce chances for him. We need to change this."
One United player who looked less than happy with his afternoon’s work was Juan Mata, who had been introduced to the fray with 25 minutes remaining, only to be subbed himself in added time.
But Mourinho played down talk of a rift with the Spain forward, explaining he made the substitution to steel his side against a Leicester comeback.
"Juan played well," Mourinho said. "He gave me exactly what I need. I have to take the smallest player off because the game will end in long balls."