Arsenal have a number of injury issues to deal with when they return to Premier League action against Wolves this weekend.
Unai Emery’s side secured their spot in the last 32 of the Europa League with a 0-0 draw against Sporting Lisbon on Thursday and now turn their attention back to domestic duties.
"He was working well and he was having a good match. He had some chances too.
"When you are playing football, when you are playing in competitive matches, it can happen. You don't want it to happen but this is our profession.
"Now he is at the hospital. The news is that we are going to wait - but we think it's a serious injury."
Arsenal are yet to reveal the full extent of the problem, with Welbeck having required oxygen on the pitch after landing badly on his right ankle.
Arsenal team news: Danny Welbeck suffered a serious ankle injury against Sporting Lisbon (Image: GETTY•buildlineup.com)
Arsenal team news: The Gunners striker is in hospital after falling awkwardly (Image: GETTY)
He was carried off the field with his leg in a protective brace, surrounded by up to 10 medical staff as he received treatment.
Meanwhile, Lichtsteiner pulled up with an apparent hamstring injury and is now doubtful for the clash with Wolves.
The Swiss veteran joins Mohamed Elneny and Konstantinos Mavropanos on the treatment table while Laurent Koscielny and Emile Smith Rowe are also doubtful.
Nacho Monreal was not fit for the midweek clash but will hope to feature against Wolves, potentially replacing Sead Kolasinac at left-back.
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Arsenal team news: Is this how Unai Emery's side will line up against Wolverhampton Wanderers? (Image: buildlineup.com)
Danny Welbeck injury the 'worst news' for Arsenal says Emery
Matteo Guendouzi is available once more after his one-match suspension, while Alex Iwobi and Henrikh Mkhitaryan will compete for a spot on the right flank.
Hector Bellerin, Shkodran Mustafi, Lucas Torreira, Mesut Ozil, Pierre-Emerick Aubameyang and Alexandre Lacazette were all rested on Thursday, suggesting they will return here.
Arsenal predicted line-up vs Wolverhampton Wanderers