Arsenal boosted their hopes of a top-four finish in the Premier League after a bizarre 10th-minute goal by striker Pierre-Emerick Aubameyang gave them a 1-0 win at 10-man Watford on Monday.
The result lifted the Gunners two places up to fourth on 66 points from 33 games, one behind third-placed Tottenham Hotspur. Arsenal are ahead of fifth-placed Chelsea, who have played a game more, on goal difference. Watford stayed 10th with 46 points.
Arsenal manager Unai Emery was pleased with his team's first away clean sheet of the season.
"A clean sheet is very important," he told the BBC. "It is going to give us a lot of information, this match."
The fast-paced clash took a decisive turn in a frantic one-minute spell early on, as Aubameyang found the back of the net in unlikely fashion before Watford striker Troy Deeney was shown a straight red card for elbowing Lucas Torreira.
The home side's goalkeeper Ben Foster dwelled on Daryl Janmaat's back pass for too long, allowing Aubameyang to close him down and block his attempted goalmouth clearance as the ball ricocheted into the back of the net.
Foster made no excuses for his howler.
"I've said sorry to the lads," he said. "I tried to drag it on to my left and pass it out but before I knew it Aubameyang was bloody on me. He is too quick. In hindsight you have to get rid [of the ball] as quick as you can, even if it goes into row Z."
Torreira was taken off at half-time with a "small injury," said Emery, who also cited the atmosphere surrounding the Uruguay international after the Deeney incident.
"First I decided to do the change of Lucas Torreira because, after the red card, the atmosphere is against him," he said.
"Also, the doctor said to me in the first half that he has a little pain from Thursday's game against Napoli and I decided 'okay, it's the moment [to take him off]'."
Asked what he thought of Deeney's red card, the former Sevilla and PSG boss said he never saw the clash.
"I didn't see the red card. I leave the decision for the referee," he said. "It's clear it helped us, with the decisions, because we played with one more player from then on. It's more difficult for them. But our goal gave us the advantage in the first half and after the red card also."
Despite their numerical disadvantage, Watford kept pressing and missed a string of chances to draw level, having twice been denied by the woodwork as well as by some good saves from Arsenal keeper Bernd Leno.
The home team's manager Marco Silva praised his team for their fighting spirit in the face of adversity.
"We did a lot of things to try to win, a big effort," he said. "We didn't get any points but we played well. It was a difficult game with 10 men."