Bolton Wanderers midfielder Fabrice Muamba was hospitalised after collapsing on the pitch during the FA Cup quarter-final at Tottenham Hotspur on Saturday.
Players, clubs and fans showed their support for Muamba on Twitter.
Tottenham manager Harry Redknapp:
"Praying for Fabrice Muamba. A very very sad day. Hope the young lad pulls through."
Arsenal captain Robin van Persie:
"I'm so sad about what happened to Fabrice Muamba today. Played with him 4 a couple of years. What a great guy. Always a smile on his face."
Former Bolton goalkeeper Ali Al-Habsi:
"All our hearts with Fabrice Muamba, one of my closest friends at Bolton.. Im shocked, wishing him a fast recovery."
Juventus midfielder Andrea Pirlo dedicated his side's 5-0 win over Fiorentina to Muamba:
"He's our colleague, we pray he gets well soon."
Barcelona midfielder and former Arsenal captain Cesc Fabregas:
"My thoughts are with Fabrice and his family. Stay strong mate. Our prayers are with you."
Manchester United and England striker Wayne Rooney:
"Hope fabrice muamba is ok. Praying for him and his family. Still in shock."
Tottenham defender Kyle Walker, who scored in the match against Bolton to make it 1-1:
"Doesn't matter who you support..Doesn't matter if you aren't a football fan. Doesn't matter if you aren't religious..Pray for Fabrice Muamba."
Manchester City captain Vincent Kompany:
"Critically ill and intensive care" I really hope that this nightmare will be soon over and I wish for Fabrice Muamba to recover fully."
Former Chelsea and Germany midfielder Michael Ballack:
"We want to send our prayers to Fabrice Muamba, his family, his friends and all at Bolton Wanderers."