Arsenal's tie with Sporting CP was marked by an incident that will have scared supporters, players and coaching staff. Welbeck left the pitch clearly in pain and on a stretcher after being treated by doctors on the pitch.
The 27-year-old injured his left foot as he landed awkwardly while trying to attack a header, and fell to the ground asking for assistance, who had to give him oxygen while trying to ease the pain.
Welbeck left the field on a stretcher and to the applause of the entire stadium, in what appears to be a serious injury. 'Gunners' teammate Matteo Guendouzi, in particular, seemed shocked by the incident.
The striker was also selected in Gareth Southgate's England squad on Thursday, which he will likely have to pull out of if the injury is serious.