Chelsea had been torrid for the entire first half but returned with a bang as Gallagher converted from Malo Gusto’s cross on his return to Selhurst Park shortly after the restart.
The Blues looked like they were not going to find a way through Palace’s back line until they broke in added time.
Palmer teed up Gallagher to grab the all-important second before also slotting the ball through for Fernandez to make it three.
Here is how the Chelsea players rated…