Per Mertesacker believes Arsenal stopped playing their game in the second half against Watford.

The German made his first Premier League start for a long time against Watford, coming in for the injured Shkodran Mustafi at the heart of the defence.

He headed Arsenal into the lead in the first half, but found himself under far more pressure than he would have liked in the second half.

It was a defeat with many familiar failings, and Mertesacker was brought out in front of the media to make familiar and concerning comments.

“With the injuries, especially in the second half towards the end of the game, we want to make changes to bring more energy, to make a difference at the end of the day,” he told Arsenal.com.

“I think we could have done a little bit better, when we gained possession we lost it straight away. I think we struggled a lot in terms of that and that’s not our game, you could sense that we struggled a lot in those scenes where they just regained the ball back as quickly as they could.”

Arsenal did have the chances to win the game despite not playing at their best, but Mertesacker felt Arsenal needed more to ensure that accidents wouldn’t happen.

“Yes, I think that’s what we lacked [chances to win], especially in the second half, you know when we got the ball we missed a chance, but we missed as well to play, we missed it completely.

“That’s what we did really well in the first half, where we regained possession, kept possession, that was really good. In the second half we just wasted the ball and that’s obviously not enough. If you just protect and you have no chances on the break and you miss one chance to kill the game, then it’s difficult in the Premier League to win any game.”

While Arsenal failed to kill the game off, Watford won a dubious penalty that completely altered the direction of the game. Mertesacker offered a neutral response, and instead criticised Arsenal’s response.

“I’m not sure, I cannot tell. Honestly, it’s so quick these actions, it’s difficult to judge and the referee made that decision. I think for us it was kind of a wake-up call, but it wasn’t loud enough.”

With games coming thick and fast, Arsenal can’t linger on the performance and result for too long. Mertesacker feels Arsenal simply have to do better next time.

“I mean obviously it’s important [playing in the league again], but if you want to make the difference on the pitch, you know in the second half even myself it was difficult to push. I have to do better next time, that is my target, to push these guys more that we get more out of that when we get the ball.”

Arsenal’s travel to Serbia to play Red Star Belgrade in the Europa League on Thursday, before travelling to Everton on Sunday.