Watford have ended Arsenal's bid for a third successive FA Cup title by beating the Gunners 2-1 at the Emirates Stadium this afternoon to reach the semi-finals of the competition.
Second-half goals from Odion Ighalo and Adlene Guedioura stunned the hosts, who pulled one back late on through Danny Welbeck, but it was not enough to salvage the defence of their crown or alleviate any pressure on under-fire manager Arsene Wenger in North London.
Arsenal must claw back an eight-point gap on Leicester in the Premier League, or reverse a 2-0 first-leg deficit to Barcelona in the Champions League, if they are to keep alive their trophy ambitions.
It proved a fast and furious start from Arsenal, who had the ball in the net inside 10 minutes through Olivier Giroud following a slick passing move, but it was correctly ruled out for offside.
Wenger's side continued in the same vein but, despite their possession and general dominance, clear-cut chances were at a premium, with goalkeeper Costel Pantilimon - who replaced Heurelho Gomes in the lineup minutes before kickoff - going largely untested.
It was referee Andre Marriner who stole headlines in the first 28 minutes when he could, and arguably should, have dismissed Gunners defender Gabriel for a two-footed lunge on Troy Deeney, but the Brazilian emerged without so much as a talking-to for the challenge.
Moments later, Arsenal almost had the breakthrough, but Mohamed Elneny, played in by Calum Chambers, sliced horribly wide of Pantilimon's goal as Watford - and perhaps Marriner - could breathe a sigh of relief.
The Hornets, without a win over their fellow Londoners since 1988, did have their moments, but dithering in possession from Ighalo at key times saw several promising attacks break down throughout the opening half.
At the other end, a sublime bit of skill from Mesut Ozil saw the lively Joel Campbell tee up Elneny on the edge of the box, but the former Basel man blazed over in what proved the last chance of an entertaining, if controversial, first half.
Arsenal, unbeaten in the FA Cup since 2013, saw their stellar record in this competition heavily threatened within five minutes of the restart when Ighalo swivelled Gabriel and poked past David Ospina from six yards to stun the hosts and their 52,000 fans in attendance.
Despite their advantage, Watford refused to rest on their laurels - and their sense of adventure was rewarded on 64 minutes when Guedioura, after brilliant hold-up play from Deeney, smashed past Ospina at his near post from an almost impossible angle.
A desperate Wenger, whose future in North London was already a focus of discussion in recent weeks, deployed Theo Walcott, Welbeck and Alex Iwobi in a treble substitution.
With two minutes remaining, Welbeck threw his side a lifeline with a cool finish beyond Pantilimon, but the former Manchester United man missed a gilt-edged chance moments later, firing over an empty net after Iwobi's drive came back off the post.
It was as close as Wenger's side would come to an equaliser as Quique Flores and co held on.
