Bukayo Saka was deemed fit to start for the visitors despite having limped off in the 4-0 win at Bournemouth in the Premier League at the weekend. However, Spanish coach Mikel Arteta made a bad decision to play him as a starter.
Another setback followed for the Gunners as the 22-year-old went down just after the half-hour mark and was unable to carry on, with Fabio Vieira taking his place.
Not only did the Emirates Stadium side lose 1-2 to Lens in the Champions League group stage match, but they also lost a key player in Arteta's squad. The manafer was asked about the striker's injury in the post-match press conference.
"It was an action. It was a backheel and he felt something specific. It was nothing else. Obviously, he wasn’t comfortable to continue. But it doesn't look good," he told reporters.