Watford had taken control of the game in the second half, after a good finish from Roberto Pereyra and a lucky strike from Jose Holebas.
Crystal Palace knew they had to turn things around quickly if they were to get anything from the game, and Roy Hodgson opted to bring on German creative midfielder Max Meyer.
Just minutes after the former Schalke man had come on to the pitch, he slid the ball through perfectly to Wilfried Zaha who was on the left side of the box.
The Ivorian timed his run to perfection, and managed to carry the ball to the goal where he cooly slotted it between the legs of Ben Foster in the Watford goal.