Fernandes arrived at Old Trafford last month from Sporting Lisbon and has impressed early on with his tidy displays in midfield.
The 25-year-old has now played three times for the club but is yet to find the net.
"He was unbelievable and with top players you can tell straight away they have something to add, he's silky on the ball," van Persie said on BT Sport after the match.
"He has that pass, he has a nice cross and shot, he's a joy to watch."
The Dutchman made 105 appearances for United between 2012 and 2015, scoring 58 goals. body check tags ::