Cardiff City manager Neil Warnock has suggested Simon Hooper should not be refereeing Premier League games after his side's 5-1 thumping by Watford on Friday.

The Bluebirds were put to the sword by a superb Gerard Deulofeu hat-trick and a Troy Deeney double, but Warnock was furious with Hooper's decision not to award a penalty when Watford were 1-0 up.

Josh Murphy appeared to be bundled to the ground just inside the penalty area by Daryl Janmaat shortly before half-time, but Hooper was unmoved.

Watford took full advantage of that reprieve, brutally punishing some wayward home defending in the second half to leave Cardiff one point above the relegation zone.

Warnock was seething with the decision not to award a spot-kick, accusing Hooper of not being up to the required level to officiate in the Premier League and claiming that officials often "guess".

"Nobody can understand it," he told Sky Sports.

"Decisions like that change the game. I can't understand why it wasn't given. It's a blatant penalty.

"It's no excuse for conceding five but everyone in the game knows it changes things.

"The referee is in a great position so I just can't understand it. If you can't give decisions like that at this level, you shouldn't be refereeing."

He later told the BBC's Match of the Day: "Whether they are educated correctly I don't know, but it's a clear penalty.

"Deep down I think all the officials knew really. I don't understand at this level why things like that can't be given.

"There will be mistakes but they will get much more right with VAR. I think the referees guess a lot of the time and you can't do that at this level."

Warnock’s counterpart, Javi Gracia, conceded that Cardiff have every right to be aggrieved with the decision, but the Spaniard preferred to focus on his side's swaggering performance instead.

"I understand," he said. "They can be angry with that, but I prefer to not say anything about that.

"We played very well, scored five goals and dominated the game. We deserved this victory. It was a very good performance. To win here is not easy. I am very proud of all my players."

Deulofeu was in irresistible form throughout, doubling his tally for the season with three sumptuous finishes.

His strike partner Deeney said: "This player is top drawer. You can see why everyone wants him. He has missed chances in previous games but has never shied away and always tries to improve.

"You can only ever admire that. He deserves all the credit he will get. Today it was all about this guy and nothing to do with me."