Arsenal lost the chance to seal top spot after succumbing to a 2-0 defeat at the hands of PSV Eindhoven.
The Gunners only needed a point in the Netherlands to advance to the last 16 as group winners but will now have to beat FC Zurich in their last game to seal the top spot ticket.
Joey Veerman put the visitors ahead with a first-time finish from 16 yards in the 55th minute
Former Barcelona striker, and aerial-ball specialist, Luuk de Jong came off the bench to double the lead eight minutes later after a mistake by keeper Aaron Ramsdale on his European debut.
The loss is Arsenal’s first loss in Europe this season.