Unai Emery explains the substitution and tactical changes of Lucas Torreira against Watford

Unai Emery eased fears of key midfielder Lucas Torreira.

The 23-year-old was fired at half-time, with Arsenal pushing Watford back to strengthen his four hopes.

Fans were worried that he would not reappear after the break.

But Emery said the midway move of the 1-0 win was a precaution ahead of Thursday's Europa League clash against Napoli.

He says it was more due to the fact that he was at the center of the red card incident that had seen Troy Deeney take a red card than any other blame.

"I first decided to change Torreira because after the red card, the atmosphere was against him," he said.

"Also, the doctor told me in the first period that he had a little pain like Thursday and that I decided" OK, it's the moment ".

"We were playing with the same system, 4-2-3-1, with Aaron Ramsey and [Granit] Xhaka gets closer to the room and Mesut [Ozil] like a # 10.

"We did not control how I wanted the game and I thought that doing with three central defenders may be enough with our accumulation, we use a player in the middle, like Matteo. [Guendouzi], helping with Xhaka, Aaron and Mesut, to make clearer the superiority to the midfield.

"But in reality, I did not make the right decision on the ground, we did not have the control I wanted," he added.

"After changing to 4-2-3-1 with Ainsley [Maitland-Niles]. Above all, our team was worried, because in the second half, they can take a few moments, the possibility of scoring points and actions in second position.

"We worked well on the set pieces, we worked well on the second action and the long ball, the most important thing for us was to score the second ball for more control."

Pierre-Emerick Aubameyang scored the only goal of the match, capitalizing on an error by Watford goalkeeper Ben Foster.