Jose Mourinho brought Marouane Fellaini on as a substitution and it was he who grabbed a late winner for Manchester United against Arsenal.
What a blow for Wenger to lose his final outing at Old Trafford as Arsenal boss (sixth away defeat in a row) to Mourinho. And it was done by a tactical switch.
Moments earlier, Marcus Rashford had a goal correctly ruled offside when another Fellaini header bounced off the striker and into the net.
Ta ra, Wenger! Three points in the bag for United with second place almost secured.