Mikel Arteta revealed he gave his Arsenal players a rousing half-time pep talk as they fought back to keep their hopes of reaching the Europa League final alive following a narrow defeat in Villarreal.

The first leg of this semi-final clash appeared to be getting away from the Gunners as first-half goals from Manuel Trigueros and Raul Albiol preceded a Dani Ceballos red card just before the hour.

But Nicolas Pepe converted from the spot to send Arsenal home with a 2-1 deficit, Villarreal having also been reduced to 10 men late on following the dismissal of former Tottenham man Etienne Capoue.

Having gone in two goals behind at the interval and seeing a penalty award overturned due to a VAR review deeming Pepe had handled the ball, Arteta told his players they needed to react before it was too late.

Asked about the mood in the dressing room at full-time, he said: ‘Well comparing how it was at half-time, it is very different.

‘I said to them: ‘We have an opportunity. It is a big challenge what we have ahead of us, but we have the opportunity to make it. But it has to be now. In the return leg it is going to be too late. We have to change it right now. If we are able to do that we are going to get here in a completely different position’.

‘We still had another incident, which was the red card and playing with 10 men against this team, and the team went to a different level again and we got the goal.’

Arteta opted to play a different formation with no out-and-out striker as the visitors struggled to create chances from open play.

Captain Pierre-Emerick Aubameyang came on late in the game having recently recovered from malaria and had a good chance to equalise – with Arteta left defending his tactical approach.

‘It is the way we prepared the game, it is the decision that I made, thinking that it was the best way to play,’ he said of adopting a strikerless system.

‘But the game was changed after four minutes (with the first goal) so it is difficult to assess whether it would work or not.

‘Conceding the set-piece (for Albiol’s goal) as well changed it and after we have to approach it in a different way.

‘(Aubameyang) was very unlucky because I think he slipped just before he took the shot and at the end it didn’t go through. But that was a big, big chance obviously.’

This is Arsenal’s third Europa League semi-final in four years but they have only made the final once in that time – under current Villarreal boss Unai Emery, who looked to be getting one over his former club as the hosts made a flying start.

Trigueros opened the scoring inside five minutes, driving home a low effort after indecision in the Arsenal box allowed Samuel Chukwueze to play in his team-mate.

Arteta was left ashen-faced as the lead was doubled before the half-hour, Albiol turning home at the back post as Arsenal failed to get anywhere near a routine corner.

But despite Ceballos being sent off, the second half offered hope for the visitors as Pepe levelled with a penalty that Emery was furious to see awarded.

‘We need to keep our hopes high,’ he said of taking his team to the final.

‘There are many circumstances that can affect you one way or another. After a good first half we went in 2-0 up, then they were dominating the game in the second half.

‘Then there was a key moment in the game with a penalty that is not a penalty, VAR should be able to give justice in such a clear-cut situation when a penalty was never a penalty.

‘I’m unhappy about that – certain details escape your control, like the referee, and once the match is finished you put all the cards on the table and we should say that we won the first match.’