Fernandes could have wrapped up a first-half hat-trick when Ole Gunnar Solskjaer's side were awarded a penalty in the 35th minute, but the Portuguese midfielder allowed Rashford to step up and take the spot kick.
Rashford made no mistake from 12 yards as the Red Devils ran out 4-1 winners at Old Trafford, and Fernandes has since explained why he gave up his pursuit of a hat-trick to allow Rashford to get his name on the scoresheet.
Speaking to BT Sport after the game, Fernandes said: "That's not the point. Of course, every player wants to score a hat-trick. But after the game in the Premier League I told Rashford he would take the next one.
"So I remembered that, and also because Rashford is one of the top scorers in the Champions League. I think it will be important for him to keep going there and take that confidence.
"But as I say, it doesn't matter who takes the penalties, the most important thing is scoring. The team scores. When the team scores, I score too."
United's victory on Tuesday evening puts them in control of Group H with two games remaining, and next up for Solskjaer's side is a visit to Southampton in the Premier League on Sunday. body check tags ::