Manchester City have confirmed Scott Sinclair is being treated for a blood clot in his shoulder.
Sinclair, 24, did not travel with Roberto Mancini's squad to face his former club Swansea after being taken ill during training on Friday.
Sinclair is understood to be in a comfortable condition and his illness is not life-threatening.
The club tweeted a get-well message to the former England Under-21 international, and manager Roberto Mancini said: "Scott had a problem yesterday, I don't think it is a bad situation and it is under control."