Manchester City manager winger Scott Sinclair was in hospital on Saturday for a treatment on a blood clot on his shoulder.
Sinclair, 24, did not travel with Roberto Mancini's squad for Saturday's 0-0 draw at his former club Swansea after being taken ill during training 24 hours earlier.
Sinclair is understood to be in a comfortable condition and his illness is not life-threatening.
City 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."
Mancini expects to know more about Sinclair's condition within the next 48 hours, but the problem caps a difficult first season at Eastlands for the former Chelsea player.
Sinclair has made just two Premier League starts for City and would appear unlikely to play in next Saturday's FA Cup final against Wigan at Wembley.