Odion Ighalo and Adlene Guedioura took the wheels off the Arsenal juggernaut that had blitzed its way through 15 unbeaten rounds of the Emirates FA Cup.
Danny Welbeck pulled a late goal back and Alex Iwobi hit the post in added time but a 2-0 quarter final loss to Watford means there will be no third successive FA Cup Final at Wembley for Arsene Wenger’s men.
Instead, the Hornets – triumphant over Arsenal for the first time in the Premier League era – upset the applecart to leave the men from the Emirates with two almost impossible tasks to rescue their season.
Arsenal 1-2 Watford
Emirates FA Cup
Sunday 13 March
First they must overturn a 2-0 Champions League deficit against Barcelona and then pursue their chase for the Premier League title.
Ighalo struck in the 50th minute after Watford has struggled in the first half. The Hornets’ top scorer turned Gabriel beautifully eight yards out after Troy Deeney knocked on a long throw-in.
The striker almost nabbed two more goals from Allan Nyom and Nathan Ake crosses before Guedioura’s fearsome 64th-minute strike.
Ighalo was involved again, this time feeding Deeney who set up Guedioura for a quite stunning angled drive that flew past the startled David Ospina.
Olivier Giroud put a second-half header over and sub Welbeck came good with his 88th-minute consolation. And there was time for fellow sub Iwobi to find the woodwork and for Welbeck to go perilously close.
But it simply wasn’t meant to be as Arsenal’s proud FA Cup record hit the buffers.
The first half belonged to Arsenal, especially in the closing stages when they really should have gone ahead.
Four minutes before the break Mesut Ozil broke free from two defenders and laid on a smashing ball to Joel Campbell deep in the danger zone.
Campbell set up Mohamed Elneny only for the Egyptian to blaze wastefully over.
Then another piece of Ozil magic allowed Campbell a shot and he, too, should have done better than poke the ball over the bar.
Arsenal bossed the play and a booking for Watford keeper Costel Pantilimon for time wasting was indicitive of the pressure the visitors were under.
The Gunners began at a gallop with Callum Chambers to the fore. One cracking early low cross from the right-back just eluded Giroud before Watford had actually touched the ball.
Giroud found the net in the 10th minute but was ruled offside.
The Hornets first effort after 12 minutes saw Ighalo’s angled shot blocked by Per Mertesacker.
Watford were caught on the break on the half hour when Mertesacker found Elneny from deep. Again, the midfielder timed his run but shanked his shot big time.
That was about it for the Hornets at that stage - but, wow, how they came flying out of the traps for the second half.
Even their most ardent fan must have wondered if they could possibly worry Arsenal.
But they did - and how - to leave Wenger contemplating more heartache and criticism as his season threaten to unravel horribly.
Arsenal (4-4-2): David Ospina; Calum Chambers, Per Mertesacker, Gabriel, Kieran Gibbs; Joel Campbell, Frances Coquelin, Mohamed Elneny, Mesut Ozil; Olivier Giroud, Alexis Sanchez.
Substitutions: Alex Iwobi for Elneny 67, Danny Welbeck for Campbell 67, Theo Walcott for Giroud 67.
Substitutes not used: Nacho Monreal, Mathieu Flamini, Hector Bellerin, Matt Macey.
Watford (4-5-1): Heurelho Gomes; Allan Nyom, Sebastian Prodl, Craig Cathcart, Nathan Ake; Adlene Guedioura, Ben Watson, Etienne Capoue, Valon Behrami, Troy Deeney; Odion Ighalo.
Substitutions: Ikechi Anya for Capoue 73; Almen Abdi for Guedioura 76; Nordin Amrabat for Ighalo 83.
Substitutes not used: Mario Suarez, Jose Manuel Jurado, Obbi Oulare, Nordin Amrabat, Heurelho Gomes.
Goals: Ighalo 50, Guedioura, 64
Referee: Andre Marriner