Palace frustrated United for much of the game but were unable to stop Fred's looping winner in the 77th minute.
It marked a debut win for new manager Ralf Rangnick and Fernandes said: "We had to carry on with what we did in the last game against Arsenal.
"We are happy because we got the three points. The results could have been even better.
"Fred has these moments, one shot per year. Everyone is happy for him because he's such a nice guy. He works a lot and people don't talk about him. He deserves the praise.
"I think it depends on the game, sometimes you have to press more, sometimes less. But everyone knows the manager wants more pressing from us.
"The first 25 minutes was unbelievable, great tempo. We could have scored so many in the first half.
"We have to follow our new manager's instructions. Now we go again to the Champions League."
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