The Arsenal forward's career has been plagued by injuries, and this could be the worst of the lot.
That was the last of the meaningful action as Arsenal failed to score for just the second time under Emery - but it will be Welbeck's injury that dominates the fall-out.
Welbeck's teammates' reactions spoke volumes as he was attended to by physios on the pitch at the Emirates.
Danny Welbeck appears to have picked up yet another serious injury.
"He has been taking to the hospital".
The England global joined Arsenal from Manchester United in 2014 for around £16m.
After the match, Unai Emery stated that he believed the injury had an impact on his players during the 0-0 draw with Sporting Lisbon. "His injury was with the mentality of the players". First it's in your mind - you think for the player.
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The 27-year-old England global was carried off on a stretcher during the goalless draw at Emirates Stadium.
"But when you are playing football in competitive matches it can happen".
It remains unclear whether Welbeck will be able to play for Arsenal again before his contract expires in the summer.
"Danny is a tough lad, so if he's on the floor, I know it's something serious".
Rob Holding: "I didn't see it because obviously I'm at the other end of the pitch so I didn't see exactly what he'd done. He can come back strong".
Welbeck pulled out of the England squad to face US following his injury, having been named in the 28-man squad earlier in the day. "Will need [to be] imaged #AFC".