The Red Devils had to work very hard to get three points in the group stages on Thursday.
United had to come from behind to beat Viktoria Plzen in the Czech Republic, with Rasmus Hojlund getting both goals.
"They (Viktoria Plzen) made a good pressure, they got the goal," Fernandes told TNT Sports.
"But the most important thing: we had the resilience, the fighting spirit, to come back.
"It was a good performance overall. Obviously, I think in the final third, we could have kept the ball a little more, but we knew the man marking from them was difficult to get away (from), so sometimes it was just a more pass and run, pass and run, to try and find the gaps."
He added to MUTV: "We should have done even a little bit better at the end.
"We had two or three transition moments where we could have killed the game. But also, when we don't kill, we have to run back quick, and we did it a lot of times."
"We want to go through," he continued.
"We want to be in the highest positions so we can avoid playing one more game, two more games in this case, and we have to win the games we have ahead."
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