Arsenal suffered defeat for the first time this season, losing 2-1 to Lens in their Champions League group stage match on Tuesday night.
The Gunners, unbeaten in their previous 11 matches, took the lead through Gabriel Jesus.
But they were equalized by Adrien Thomasson following David Raya’s poor pass behind him.
Mikel Arteta’s side, looking rusty, failed to create too many clear-cut chances and paid the price when Sepe Wahi headed home Lens’ winner with just over 20 minutes remaining.
Kai Havertz, Leandro Trossard, Reiss Nelson and Emile Smith Rowe have all but enriched Arsenal’s accounts.
Arsenal fell to second place in the table, one point ahead of Sevilla after drawing with PSV Eindhoven.
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