Nicolas Pepe's second-half penalty gave Arsenal renewed hope of reaching the Europa League final despite a semi-final first-leg loss at Villarreal as both sides finished with 10 men.
With the Gunners trailing 2-0 and a man down following Dani Ceballos' sending off, Pepe stepped up and fired home a precious away goal from the spot after Bukayo Saka had been tripped in the box.It means Mikel Arteta's side go into next Thursday's second leg with genuine hope of reaching a second Europa League final in three seasons and with the potential of qualifying for next season's Champions League.
They appeared to be sinking without trace when Manu Trigueros fired in an early low, angled drive for the home side before Raul Albiol slammed home at the back post following Gerard Moreno's flick-on from a corner.
Ceballos' red card with 30 minutes left, courtesy of a second booking for standing on the boot of Daniel Parejo, looked to have sealed their fate.
But Bernd Leno produced two good saves to keep the home side at bay before Pepe - playing as a false nine - had his say.
Villarreal may still have fancied their chances of scoring again, but this was hampered when they too were reduced to 10 men, as Etienne Capoue shown a second yellow for a late tackle on Saka.
The 'Yellow Submarine', managed by ex-Gunners Unai Emery, will go into the second leg on top, but facing the prospect that just one unanswered concession will send them out.Arsenal down but not out
Emery is all too familiar with the regular inquests that greet Arsenal's failures on the pitch from his 18 months in charge of the club as successor to Arsene Wenger.
It was the heavy defeat to Chelsea in the final of this competition in 2019 that was the beginning of the end for his largely disappointing stint as boss.
It felt like another inquest was incoming, this time for Arteta, with the Gunners trailing 2-0 after a half in which they were out-thought and out-classed, with their only fleeting positive moment a penalty overturned by VAr for handball against Pepe in the build-up.
Defeat in this tie would likely prompt a new level of soul-searching at the club, who currently sit 10th in the Premier League and need to triumph in this competition to extend their record of appearing in continental competition to 26 successive seasons.
The Gunners' current boss has built a more robust, patient side than his predecessor, but they badly let themselves down with two defensive lapses to hand the initiative to their opponent.
Samuel Chukwueze was allowed to carry the ball too far into the box to tee up the first goal for Trigueros after just five minutes. Even more criminal was the lack of marking that allowed Moreno to flick the ball on for Albiol to score the second.
Chasing that crucial away goal, they could ill-afford Ceballos' disciplinary lapse, and it almost proved terminal to their hopes with Moreno twice seeing efforts saved by Leno in the aftermath.
To the credit of Arteta and his players, though, they continued to push for a foothold and found it when Saka went down in the box. The amount of contact from Trigueros' boot is up for debate, although VAR backed up the on-field official.
It could have been even better for the Gunners, but substitute Pierre-Emerick Aubameyang was denied by a fine save from Geronimo Rulli, leaving Pepe's goal as their sole reward.
Pepe has not always stood out as the man for the big occasion during his time at Arsenal, but with a goal in each of his last three Europa League games and six in total in this season's competition, he is leading from the front in this campaign.
His strike on Thursday could well be the most important of the lot - a goal in times of adversity that could well allow Arsenal to salvage something from the season.
'Confident we have a chance to win'
Arsenal boss Mikel Arteta on BT Sport: "We didn't want to come here and lose but after the way the game developed, you have to take the result. If you have to lose it is probably the best result we could have.
"Two different halves. We started to be us, in the first half there were so many moments we weren't.
"We started to chase and were not precise with the ball, didn't have enough control. We didn't have enough threat or desire to attack the box, in the second half it was completely different.
"We are very used to that (Bukayo Saka playing well) this season, but it tells us we need to do much more as we cannot always rely on him. Bernd Leno was very good, at 2-0, the chance with Gerard Moreno, he saved us.
"I am confident we have a chance to win."
Arsenal suffer rare first-leg loss
--This was just the second time in their 10 European semi-finals that Arsenal have lost the first leg, also doing so in the 2008-09 Champions League against Manchester United (from which they were eliminated).
--Villarreal have progressed from 15 of their 16 two-legged ties in major European competition when winning the first leg - the only exception was in the 2015-16 UEFA Europa League semi-final, when they went out to Liverpool despite winning the first leg.
--Arsenal have been shown 10 red cards in all competitions under Mikel Arteta, twice as many as any other Premier League side in the period since he took over in December 2019.
--This was the first time a former Arsenal manager (Unai Emery) had beaten the Gunners since George Graham's Tottenham side won 2-1 at White Hart Lane in a Premier League encounter in November 1999.
--Manu Trigueros' opener for Villarreal at 4m 39s was the earliest European goal Arsenal have conceded since September 2016, when Edinson Cavani scored after 42 seconds for Paris Saint-Germain in the Champions League.
--Arsenal's Nicolas Pepe has been involved in more goals in the UEFA Europa League this season than any other player (10 - 6 goals, 4 assists).
--Gerard Moreno has scored or assisted a goal in all seven of his UEFA Europa League starts for Villarreal this season, with the Spaniard setting up the second goal this evening.
--Arsenal's Dani Ceballos picked up his first red card in all competitions for a team playing in the top five European leagues (201st game).