After losing their opening two matches of the season, Arsenal have won 12 and drawn three of their 15 games in all competitions since, including a run of 11 straight victories between August and October.
The forward landed badly after challenging for a header and needed to be stretched off the pitch after some lengthy treatment, which included him requiring oxygen.
Unai Emery admitted the injury had an adverse affect on his players - although the Emirates stalemate was enough to seal progression into the latter stages of the Europa League. We wish him all the best in his recovery.
"I feel there's a good mix between discipline and freedom", added the German, who has featured in all of Arsenal's 11 Premier League matches, including the 1-1 draw against Liverpool on Saturday.
Arsenal fans and spectators have also taken to social media as they reacted to the painful injury suffered by the Gunners' winger.More news: One critical after multiple stabbings ‘incident’ in Melbourne
"I was hoping to score soon because I came back late from the World Cup and I was lacking maybe a bit of efficiency and luck but you always need to keep working hard and keep the faith and that´s what happened tonight", France striker Giroud told BT Sport.
"Now he is at the hospital". "We think [they are] serious injuries".
The result saw Arsenal qualify from their group, but the achievement was overshadowed by Welbeck's setback.
"Danny is a very good person, his commitment with us is very big. We are following him every match and know he will help us in the future".
Welbeck collapsed in pain after a collision in the Sporting penalty area 25 minutes into the game at the Emirates and immediately waved for medical attention as he writhed on the ground.