It was a tough night for Arsenal, who looked off the pace as a run of nine Champions League group games unbeaten was ended by a buoyant Lens.
Sloppy in defence, the Gunners struggled to create clear-cut chances – and will look to bounce back when they travel to Sevilla in three weeks’ time.
However, the departure of Bukayo Saka will be the biggest concern when the dust settles.
He was doubtful for the 4-0 win over Bournemouth at the weekend, but started – before being withdrawn after 76 minutes. Saka was passed fit for this match, but went off in discomfort.
Before his substitution, the forward showed his quality once more by providing the assist for Gabriel Jesus’ strike and became the first player to record five goals and five assists this season for a team in Europe’s big five leagues.
He later emerged around the hour mark and sat on the bench with his team-mates to watch the rest of the match.
But, while Mikel Arteta said he had no regrets, questions will be asked about his decision to risk Saka, especially if he is absent when champions Manchester City visit Emirates Stadium in the Premier League on Sunday.