Arsenal midfielder Aaron Ramsey appears to have broken his leg in a challenge from Ryan Shawcross during Saturday's 3-1 victory at Stoke and could need emergency surgery.
Arsenal manager Arsene Wenger said after the Premier League match that Ramsey would be transferred to a hospital in London.
"We know it's a bad injury - we don't know how long he will be out but it's certainly long term," Wenger said. "I'm not very happy with the tackle. We know what we are expecting, a battle everywhere. But we have now lost three players (Eduardo da Silva and Abou Diaby) on horrendous tackles and I refuse to believe it's always coincidence.
"I don't believe it when you are hit as many times as we are. I just believe in what I see and when you see a player getting injured like that it's not acceptable."
Shawcross was sent off and left the pitch in tears after seeing the extent of Ramsey's injury.
"We are not protected enough. We are sometimes victims," Arsenal captain Cesc Fabregas said.
The game was level at 1-1 when the incident occurred but Arsenal scored a late penalty through Cesc Fabregas and an injury-time goal from Thomas Vermaelen.
