The 25-year-old only played the final nine minutes of Thursday's clash, but Van Persie has said that the January arrival "was unbelievable" and "a joy to watch" during his time on the field.
"He was unbelievable. With top players you can straight away tell he has something to add. He is silky on the ball, he has the pass, he has a nice cross and shot. So a joy to watch," Van Persie told BT Sport.
Fernandes has started both of United's Premier League games against Wolverhampton Wanderers and Chelsea since arriving from Sporting Lisbon last month.
The Red Devils, who will welcome Brugge to Old Trafford for the second leg of their last-32 tie next week, are back in league action at home to Watford on Sunday afternoon.