Welbeck has always been Arsenal's go to man on Europa League nights, scoring five goals in his past 13 appearances in the competition, but he looks set for a lengthy spell on the sidelines after landing on his ankle awkwardly.
Henrikh Mkhitaryan of Arsenal crosses during the Europa League match at the Emirates Stadium.
The 27-year-old was hurt in the 25th minute when he jumped for a header and landed badly on his right ankle.
Record five-time winners Sevilla needed a late penalty from Ever Banega to claim a 3-2 victory at Akhisar Belediyespor, after having a man sent off, losing a two-goal lead and seeing the Turks miss a spot-kick of their own. Welbeck fired the ball on target but keeper Reman Ribeiro was equal to the task which led to the Longsight-born attacker remain down, before eventually being carried off to be replaced by Pierre-Emerick Aubameyang after a lengthy stoppage.
Arsenal had already beaten Thursday's opponents in this season's tournament, triumphing 1-0 in Portugal last month, and Emery said the draw at the Emirates had demonstrated the significance of securing that prior win in Lisbon.