Danny Welbeck could face a lengthy spell on the sidelines after Arsenal described his ankle injury as "significant".
Welbeck was carried off on a stretcher on the half-hour mark of Thursday's Europa League stalemate with Sporting Lisbon.
The England forward continues to be assessed, with the Gunners set to provide a further update on his condition in the next 72 hours.
He is expected to miss his country’s fixtures against the United States and Croatia during the upcoming international break, having been named in Gareth Southgate’s squad earlier on Thursday.
“Danny remains in hospital and will continue to be assessed,” the club posted on arsenal.com on Friday afternoon.
“A further update will be issued over the next 72 hours.”
Welbeck has endured a wretched injury record during his career with knee issues costing him months on the sidelines.
His latest setback comes after he landed badly on his right ankle having jumped for a header in the 25th minute of the Group E encounter at the Emirates Stadium.
The 27-year-old received oxygen on the pitch and had his leg in a protective brace as he was taken off.
Qualification assured
Gunners head coach Unai Emery admitted after the goalless draw – which assured Arsenal’s qualification for the knockout stages – that Welbeck’s injury weighed heavy on his players.
Team-mate Rob Holding has backed Welbeck to make another comeback and insists the Arsenal players will rally around their colleague.
“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,” said Holding.
“But Danny is a tough lad so if he’s on the floor, I know it’s something serious and he’s gone off to hospital now and we’ll see what happens.
“He’s been so unlucky with injuries over the past few years but he’s a good character and got a good set of lads around him so we’ll lift him up and get him back as soon as we can.
“He can come back strong.”
