Boss Mikel Arteta says Premier League leaders Arsenal must “reset” after losing to PSV Eindhoven and missing out on top spot in Europa League Group A.
The Gunners needed just one point in Holland to progress to the last 16 next March.
But Joey Werman’s first-time finish from 16 yards and substitute Luc de Jong’s header – after a mistake by keeper Aaron Ramsdale on his European debut – meant Arsenal lost in Europe for the first time this season.
“I’m very disappointed,” Arteta added.
“We were nowhere near our level and we know it’s very difficult to win in Europe. I saw a lot of guys lose energy because we had to chase the ball so much.
“It’s the end of a long run where we’ve won a lot of games and we have to reset.”
PSV, managed by former Manchester United forward Ruud van Nistelrooy, also had three goals disallowed for offside as Arsenal were well beaten.
The Gunners must beat Zurich, who they beat 2-1 in Switzerland on September 8, in their final group game next Thursday at the Emirates Stadium (20:00 GMT) to secure a place in the last 16.
If they fail to win and PSV beat Bodo/Glimt in Norway, Arsenal will face two extra games in the knockout round play-offs, which will also include teams that qualify from their Champions League. Finished third in group, including Barcelona.
