Watford’s defensive improvements deserted them in shambolic fashion as they crashed to a 4-0 defeat to Crystal Palace at a wet and cold Selhurst Park.

The Eagles, who completed the home and away double over the Hornets as a result, only had four attempts on target in the match but a number of collective and individual mistakes at the back ensured they had a 100 per cent successful conversion rate.

Watford had started encouragingly against a subdued Palace side in the first 15 minutes but once mistakes from the usually reliable Lloyd Doyley and Nyron Nosworthy had enabled Wilfried Zaha to put the hosts in front, the tone was set.

What followed were three more goals – two from Chris Martin and one for Kagisho Dikgacoi – that all originated from Darren Ambrose set pieces. All should have been dealt with – and all weren’t.

Watford weren’t four goals worse than their opponents – much of their play was at least on a par with Palace’s – but they lacked a cutting edge, with Chris Iwelumo, Joe Garner and replacement Gavin Massey rarely threatening to test keeper Julian Speroni.

Sean Dyche was forced into one change from the starting line-up that did so well to beat Leicester City in midweek. Second-half substitute and match-winner Craig Forsyth was promoted from the bench as Sean Murray was ruled out through injury. Massey was on the bench after being recalled from his loan spell at Colchester United and Jonathan Bond was also among the replacements again following Rene Gilmartin’s temporary switch to Crawley Town.

It was the visitors who had the first attempt when, following a throw, Adrian Mariappa crossed from the left and Iwelumo laid the ball back to Alex Kacaniklic, but the on-loan Fulham midfielder dragged his attempted half-volley down into the ground and the effort went harmlessly wide.

Jonathan Hogg was closer to the target with another strike from the edge of the area two minutes later after a free-kick had been half-cleared. But while Speroni was untroubled by either attempt, it was an encouraging start to the contest from the Hornets, who also won the first corner of the match during the early exchanges.

Watford had their best opening to date in the tenth minute when Garner was pushed over on the edge of the D and although Kacaniklic got his free-kick on target and up and over the wall, the Palace keeper read the set piece and saved with relative ease.

Dougie Freedman’s side offered very little as an attacking presence in a lacklustre first 15 minutes for them but that started to change when Martin played an incisive pass inside Doyley to put Ambrose in on the right, but his low centre was cleared behind for the Eagles’ first corner of the match. And from that set piece on the right, Mile Jedinak was given space to get up towards the far post but he got his angles wrong and headed wide of Scott Loach’s left-hand post.

That kick-started Palace into life and in the 22nd minute they took the lead.

With Doyley caught out by a pass down the inside right channel, the Hornets found themselves dragged out of position defensively when Jermaine Easter lost Nosworthy too easily and crossed low for the unmarked Zaha, whose firmly-struck first-time effort was straight at Loach but he was unable to keep it out in the wet conditions.

The Hornets, without being firmly under the cosh, were on the back foot following the goal and struggling to regain the assertiveness they showed in the opening stages. However, they did muster an attempt in the 36th minute when Forsyth nodded Nosworthy’s lofted pass down inside to Iwelumo, whose shot on the turn was saved by Speroni.

However, the Palace keeper was almost surprised by Forsyth’s well-struck 30-yard angled effort from the right that bounced just in front of the stopper. That could have been a memorable goal but Forsyth’s next involvement was to prove costly in another sense, although the Scot was by no means solely to blame for Palace going 2-0 up in the 38th minute.

Forsyth could have few complaints after being booked for a foul on Ambrose but the manner in which the Hornets defence dealt with the former Charlton Athletic man’s deep free-kick from the right was very poor, leaving Martin with a straightforward free header to double his side’s tally.

It was no surprise that Dyche made a change at the start of the second half, with Massey replacing the disappointing Garner, and the substitute was soon involved, putting Lee Hodson in the clear on the right for a cross that was partially cleared to John Eustace, who connected well enough with an overhead kick but was unable to direct the effort on target.

Watford had started the second half with more urgency but within five minutes of the restart they were three down following more dire defending.

The source was again a free-kick, this time from the left following a Hogg foul and this time Ambrose played the ball in low to the near post where Zaha had been allowed to take up an unmarked position. The wide man duly flicked the ball across the six-yard box, through a bemused defence and Martin was again left with a fairly routine finish for his second of the afternoon to make it 3-0.

Watford desperately needed something to give them a foothold back in the contest and an opportunity might have arisen in the 57th minute when Massey was upended near the edge of the area. But Mariappa hit the wall when the free-kick was teed up for him and was then rightly booked after cynically taking out Zaha, who was breaking clear on the counter.

But a bad afternoon duly got even worse for the Hornets in the 63rd minute when Palace netted their fourth – and again it came from a set piece.

Yet again Ambrose was the supplier, this time with a corner into the near post from the left and Dikgacoi got the better of Hogg to head towards goal but it was the actions of Easter that probably caused Loach to concede, as the striker swung and missed at the ball directly in front of the Hornets keeper.

After Zaha and Martin had made way for Sean Scanell and Glenn Murray, Hogg wasn’t too far away from helping his side to concede a fifth as his header back towards goal forced Loach to race from his area and the keeper’s clearance struck Scannell and rebounded wide.

Mark Yeates replaced Forsyth with 16 minutes remaining and his arrival coincided with a torrential downpour. But Yeates did provide a dangerous low cross from the left that saw Paddy McCarthy frantically scramble the ball narrowly wide of his own far post, with Massey ready to pounce.

Freedman gave Owen Garvan a run out for the last six minutes in place of Jedinak and the replacement almost rounded off a superb one and two-touch passing move with two minutes to go, but dragged his shot wide of Loach’s right-hand post.

Crystal Palace: Speroni; Clyne, McCarthy, Gardner, Parr; Ambrose, Dikgacoi, Jedinak (Garvan 84), Zaha (Scanell 71); Easter, C Martin (Murray 71). Not used: McShane and Price.

Watford: Loach; Hodson, Nosworthy, Mariappa, Doyley; Kacaniklic, Eustace, Hogg, Forsyth (Yeates 74); Iwelumo, Garner (Massey 46). Not used: Dickinson, Buaben and Bond.

Bookings: Forsyth for a foul on Ambrose (38); Mariappa for a foul on Zaha (58).

Attendance: 13,324.

Referee: Craig Pawson.