Cardiff rookie Adam Matthews scored his first goal for the club with an outrageous free-kick as the Bluebirds continued their prolific form against Watford at Vicarage Road.

The 17-year-old, in his first season as a professional, watched in astonishment as his 45-yard drive flew over the floundering Scott Loach and into the Watford net.

It was an awful howler from the current England under-21 goalkeeper at a crucial stage.

Peter Whittingham had given the visitors the lead with a penalty and he headed a second to make it 3-0 in the 66th minute. Jay Bothroyd then added a fourth two minutes later - Cardiff's 10th in the last two games - as the visitors cruised to victory.

For Watford, who have conceded seven in their last two games, it was another sapping defeat after their seven-game unbeaten run came to an end against Coventry on Tuesday.

Dave Jones had preferred Stephen McPhail - who starred in the 6-1 defeat of Derby on Tuesday - to the out-of-form Joe Ledley in Cardiff's midfield.

Alongside Ledley on the Cardiff bench was Ross McCormack, who made an unexpected return from a hamstring injury.

For Watford Craig Cathcart, Ross Jenkins and Don Cowie had all overcome illness to start the game. Cardiff's superior ability on the ball was quickly established with openings created for Bothroyd and Chris Burke.

And when Burke slipped the ball through to Bothroyd in the 24th minute, there was enough contact from Cathcart to justify the penalty.

With great composure, Whittingham placed the ball wide of Loach and into the bottom-left corner.

Watford's more direct approach still created some problems. Don Cowie's fierce free-kick had left the crossbar shuddering minutes earlier while Tom Cleverly forced David Marshall into a diving save from another dead-ball situation.

Michael Chopra, who scored four goals during the week, should have doubled Cardiff's lead but his predatory skills evaporated as he somehow sliced the ball wide from six yards out after Bothroyd's cross.

Cardiff's Mark Hudson, an inspiring figure throughout, then hit the post with a header as the visitors pressed hard. And they got their reward in the 41st minute.

Matthews' free-kick from just inside the Watford half appeared innocuous enough but Loach came too far and was left bemused by his misjudgement.

Cardiff continued the assault in the second half and there were more screams for a penalty when Cathcart blocked Chopra's shot on the line with suspicions of handball.

Watford responded by bringing on striker Nathan Ellington, returning from suspension.

But it only got worse for the hosts.

Firstly Whittingham headed in Gavin Rae's cross and then Bothroyd smashed his shot into the top left corner to complete the rout.

Teams:

Watford Loach, Hodson, Cathcart, Mariappa, Doyley,Cowie (Harley 79), Jenkins (Lansbury 73), Cleverley, Eustace,Graham, Hoskins (Ellington 59).

Subs Not Used: Lee, Severin, Bennett, Henderson.

Booked: Mariappa.

Cardiff Marshall, Matthews, Gerrard, Hudson,Kennedy (Quinn 57), Rae (Ledley 79), Whittingham, McPhail,Burke, Chopra (McCormack 90), Bothroyd.

Subs Not Used: Enckelman, Gyepes, Taiwo, Scimeca.

Booked: Rae, Bothroyd.

Goals: Whittingham 24 pen, Matthews 41, Whittingham 66,

Bothroyd 67.

Att: 13,895

Ref: Keith Woolmer (Northamptonshire).