Fernandes, who was named the Premier League player of the season on Saturday, had tied the record of 20 assists jointly held by former Arsenal striker Thierry Henry and ex-Manchester City playmaker Kevin De Bruyne before the final round of games.
The Portugal international broke the record on a corner in the 32nd minute when his delivery was headed home by Patrick Dorgu to give the visitors a 1-0 lead, with the United players running towards their captain to celebrate his feat.