Per Mertesacker has admitted that Arsenal were punished by Watford after failing to respond to their earlier wake-up call in the 2-1 defeat at Vicarage Road.
The German defender opened the scoring for his side in Saturday's late kickoff, only for Troy Deeney to convert after the hosts were awarded a contentious penalty.
Arsenal were unable to regain the lead in the remaining 18 minutes of normal time, and matters soon got worse as Tom Cleverley blasted home from close range to earn the Hornets all three points.
Speaking to the Gunners' official website, Mertesacker said: "Was it a pen? 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.
"I think that's what we lacked, 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."
Arsenal have now suffered defeat in three of their first eight top-flight fixtures of the campaign, leaving them sixth in the Premier League table.
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