|Aston Villa manager Gerard Houllier|
His fellow managers have wished him a speedy recovery.
Kenny Dalglish, manager of Houllier's former club Liverpool, said: "Your health is more important than anything, so we wish him well and I'm sure he is in the best possible hands."
"Doctor [Mark] Waller is there, who was the club doctor here when Gerard fell ill in 2001, so he's got a good guy beside him and I'm sure the people there will do everything they can to help.
"We won't be morose about it because we don't understand [the nature of Houllier's problem], but we send him our best wishes."
Stoke's Tony Pulis said: "Everyone in football will wish Gerard a swift recovery, we hope he is well and I am sure they will be looking after him.
"We have some fantastic medical people in this country and I am sure he will get well looked after.
"Irrespective of what medical care you get, nothing stops you from getting excited on the touchline or carrying the pressure on your shoulders if things aren't going too well. Pressure is part of the job, you get used to it."
Manchester City boss Roberto Mancini also had kind words for Houllier.
"It is not easy because, when you are under pressure, you can have some problems. But I hope Gerard comes out of hospital very quickly because he is a big person, a big manager.
"He is my friend and I hope he can be on the bench in the next game."
Fulham boss Mark Hughes added: "Our thoughts are with Gerard and his family. It's a worrying time for them and his club because he's the figurehead.
"We hope its nothing too serious."
Houllier's assistant Gary McAllister took Thursday's training session and will take charge of the squad for Saturday's game at Villa Park.
On this Good Friday, I wish Gerard well in his recovery and hope to see him back in the dugout before the end of the season.