A superb hat-trick from Watford’s Spanish striker Gerard Deulofeu and two goals from Troy Deeney gave Watford a thumping victory to increase Cardiff’s relegation worries.

Deulofeu had not scored for eight matches but he ended that draught before the break and then showed class and composure to strike twice inside four minutes on the hour mark.

Deeney made it 4-0 – set up by Deulofeu – before Sol Bamba pulled a goal back from a corner.

But Denney made the victory emphatic again with a fifth goal in stoppage time as Watford proved they might yet be good enough for European football at the end of the season.

Cardiff had won back-to-back Premier League matches in their last two games, but that did not stop manager Neil Warnock recalling his club captain Sean Morrison to the starting line-up.

The centre-back had been sidelined for four matches following appendix surgery, but he was restored to the home defence in place of Lee Peltier.

Gerard Deulofeu puts Watford ahead with his first goal of the evening (Getty Images)

Warnock made two further changes – giving Leandro Bacuna his first start since his move from Reading, while Josh Murphy was recalled in place of Bobby Reid.

Watford – who announced before kick-off they had reached an agreement for £4m compensation with Everton for their former manager Marco Silva – made seven changes from their FA Cup victory over QPR.

The rhythm that has carried the visitors into the top 10 was evident early on, however, and they gave warning to their attacking threat when Daryl Janmaat shot over after swapping passes with Deeney.

Cardiff did not lack confidence themselves, though, and when Callum Paterson chipped the ball into the path of Oumar Niasse the former Everton striker forced Ben Foster into a sharp reflex save.

But just as Warnock’s side looked capable of taking the lead, they conceded an 18th minute goal that like many this season had much to do of their own making.

Morrison, Bruno Manga and Joe Bennett all offered ineffectual tackles to Deeney on the edge of the box and when the ball broke to Deulofeu the Spaniard struck a low shot past Neil Ethereidge to put Watford ahead.

Josh Murphy puts in a challenge on Etienne Capoue (Getty Images)

It might have been extended moments later if Etheridge had not got down sharply to push a rasping shot from Deeney away for a corner.

Cardiff’s own attacking threat was infrequent although they did end the half with a surge and what appeared to be a legitimate claim for a penalty.

Murphy was released into the left-hand side of the penalty area by Niasse, only for the wing to be upended by Janmaat as the Watford player tried to recover his position.

Referee Simon Hooper, however, waved away claims for a spot-kick, much to the anger of Warnock who made a theatrical appeal to the fourth official.

It was a warning to Watford, but the visitors survived until half-time without too much further alarm.

Cardiff pushed Bacuna further forward at the start of the second-half and were more direct in trying to find Niasse and for a time it looked as though it might provide a route back into the game.

But Watford were able to reduce the home side to long shots from distance and when they roused themselves to hit Cardiff on the counter, they made the game safe with two goals inside four minutes on the hour mark.

Oumar Niasse is pulled back by Roberto Pereyra (Getty Images)

Deulofeu struck for his second after he latched onto a clearance from deep in the Watford half, following a poor free-kick from Bennett.

The Spaniard outpaced Manga over the halfway line and then sprinted forward before firing past an exposed Etheridge.

Three minutes later and Cardiff were undone again by Deulofeu, although this time the finish was even more exquisite.

Arter gave the ball away, Etienne Capoue sent Deulofeu through the middle and Etheridge was left grasping at air as the ball was delicately chipped over him and into the far corner.

Deulofeu could even have had a fourth as he again got behind Cardiff’s defence in the 73rd minute. This time, though, he unselfishly pulled the ball back for Deeney to hammer home Watford’s fourth.