WATCH: Cardiff City denied penalty against Watford. Cardiff City boss Neil Warnock was left fuming at referee Simon Hooper's decision not to award his side a blatant penalty in the 5-1 defeat to Watford. Trailing 1-0 after Gerard Deulofeu's 18th-minute strike, Cardiff were left aggrieved when Watford defender Daryl Janmaat brought Josh Murphy down in the area without any punishment. Although Watford went on to record a comfortable victory, seeing Javi Gracia's side move up to seventh in the Premier League table, it was a clear turning point in the encounter. "Everyone was talking about the penalty that hasn't been given," Warnock told Sky Sports. "Nobody can understand it. "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. "I had to calm the players down at half-time. It was just so obvious. I have never experienced anything like that really. It wasn't even a difficult decision." Later Warnock said referee Hooper owned up to making "a mistake" over the spot-kick incident. Watch the challenge in the video above.