Both Manchester-based teams were beaten in round 24 of the English Premier League, on Sunday.
Martin Odegaard scored in the second minute to start Arsenal’s 5-1 whipping of City at the Emirates Stadium.
Meanwhile, Jean-Philippe Mateta scored a double to guide Crystal palace to a 2-0 win over United at Old Trafford.
In the other result, Tottenham beat Brentford 2-0.