Fernandes made it 2-2 from the penalty spot in the 61st minute then put United ahead with a long-range strike 20 minutes later after the hosts had fallen behind twice against the Premier League's bottom team.
United had come in for heavy criticism following Sunday's FA Cup semi-final against Coventry City where they squandered a 3-0 lead before going through via a penalty shoot-out.
Fernandes told reporters that the intense demands of playing at a club like United meant winning was the only thing that mattered.
"You can be in a run of games where you win nine in a row, and when you lose one you know you'll be criticised," he added.
"Being at United demands winning every game, that's part of our job. If there is anyone in the dressing room still not used to that, they will get used to it.
"Being a Manchester United player demands being ready to receive as much criticism as praise. We receive praise when we do good things so we can't be annoyed by the criticism."
United, who had failed to win their last four league matches, moved up to sixth with Wednesday's win. They next host Burnley on Saturday.
