Arsenal moved into the Premier League top four, but made hard work of seeing off 10-man Watford 1-0 thanks to Pierre-Emerick Aubameyang’s fortunate early opener on Monday.
Aubameyang profited from an error by Watford goalkeeper Ben Foster as he blasted an attempted clearance in off the Gabon international.
Watford captain Troy Deeney was then shown a straight red card after just 11 minutes, but the Gunners failed to make the most of their man advantage and were fortunate as the hosts twice hit the woodwork.
However, Unai Emery’s men held out for a first clean sheet away from home in the Premier League this season to move ahead of Chelsea on goal difference into fourth.
Arsenal also edge to within a point of north London rivals Tottenham and two clear of Manchester United in the four-way battle for the two remaining Champions League places behind Liverpool and Manchester City.
FA Cup finalists Watford were already shorn of the man who helped book their place at Wembley against Manchester City next month as Gerard Deulofeu missed out through injury and Javi Gracia’s side did themselves little favours early on.
Firstly, Foster dallied as Aubameyang closed in to concede a comical opener.
And within seconds, Deeney was punished for an elbow into the face of Lucas Torreira.
Arsenal now have just three days to prepare for the second leg of their Europa League quarter-final away to Napoli and should have ensured an easier finish.
Aubameyang saw another effort deflected behind at the end of a sweeping counter-attack, while Foster also turned over a fierce Alex Iwobi shot.
However, the 10 men were still causing problems to a defensively vulnerable Arsenal at the other end.