Wilfried Zaha scores twice as Watford fall to a heavy 4-1 defeat to Crystal Palace in the Premier League.
For Watford, their third loss in their last four Premier League matches means they sit in 19th on 18 points and four points off safety.
Palace, meanwhile, jump up into 11th with their first win since December 28.
Mateta gave the visitors the lead in the 15th minute with a deflected strike off Craig Cathcart which wrong-footed Ben Foster in goal.
Watford responded instantly through Moussa Sissoko. The former Tottenham midfielder rose highest to a corner swung into the box and thumped his header home for his first goal for the Hertfordshire club.
Gallagher then restored Palace’s lead just before the break. Tyrick Mitchell’s cross landed at the feet of the midfielder whose first touch saw him skip by Hassane Kamara before placing his shot into the top left corner.
Watford pushed hard for an equaliser and they almost got one in the 72nd minute through top scorer Emmanuel Dennis.
Jack Butland punched a corner out and a ball was swung in by Kamara, but the Nigeria international sliced the rebound high and wide.
Palace sealed the three points in the 85th minute through Zaha who swept his shot past Foster before the Ivorian grabbed a spectacular fourth, whipping a shot into the far corner following a slick counter-attack.