Bolton Wanderers midfielder Fabrice Muamba collapsed during his side's FA Cup tie against Tottenham Hotspur this evening.
The 23-year-old is believed to have been suffering with cardiac problems and has now been taken to hospital.
His fellow footballers have taken to Twitter to offer their messages of support to Muamba.
Read their words below:
"Thoughts with Fab and his family. Feel sick watching this, puts football and everything else into perspective."
Tottenham Hotspur midfielder Tom Huddlestone
"I seriously hope my best friend in football is OK. Stay strong bro please please stay strong. God is with you remember that."
Middlesbrough defender Justin Hoyte
"I'm in shock, I really hope he pulls through. Thought and prayers are with his family."
Sunderland midfielder David Meyler
"Thoughts and prayers are with muamba and his family. Fingers crossed he's ok."
Sunderland defender Titus Bramble
"I Hope and Pray for Fabrice Muamba."
Newcastle United midfielder Ryan Taylor
"Thoughts are with fabrice muamba hope he pulls through."
Aston Villa striker Darren Bent
"Thoughts with fabrices family, we're all praying that he will be ok. Both sets of fans so respectful to the situation."
Tottenham Hotspur midfielder Jermaine Jenas
"Come on Fabrice Muamba, praying for you."
Manchester United defender Rio Ferdinand
"You gotta pull through Fab's. I was just with you last week. Come on bro."
Queens Park Rangers defender Danny Shittu
"Thoughts and prayers of all at Chelsea are with Fabrice Muamba and his family."
Chelsea Football Club
"Terrible what happened with Muamba during the game. We're all praying for him."
Tottenham Hotspur midfielder Rafael van der Vaart, who was playing in the match
"My thoughts are with Fabrice Muamba."
Manchester United striker Michael Owen
"Just heard the sad news about Fabrice Muamba. My thoughts are with him and his family right now. Puts everything in to perspective."
Queens Park Rangers captain Joey Barton
"Pray for fab god willing he will pull through"
Tottenham Hotspur striker Jermain Defoe
"Hope fabrice muamba is ok. Praying for him and his family. Still in shock."
Manchester United striker Wayne Rooney
"All my support for Muamba and his family. Everybody are with u. Really sad day for world football. Let's pray for him"
Aston Villa defender Carlos Cuellar
"Prayers go out to fab muamba great player enjoyed playing with him at under 21s, hope he is ok"
Wolverhampton Wanderers midfielder Jamie O'Hara
"Come on Fabrice stay strong bro I'm praying 4 u."
Queens Park Rangers defender Anton Ferdinand
"Everybody at Birmingham City would like to send their well wishes to Fabrice Muamba and his family at this time."
Birmingham City Football Club
"The thoughts of everyone at Queens Park Rangers Football Club are with Fabrice Muamba and his family."
Queens Park Rangers Football Club
"Sending love and hope to muamba, pray that god gives u the strength to pull thru."
Queens Park Rangers defender (on loan at Birmingham City) Peter Ramage
"Thoughts with Fabrice & he's family right now. I hope we hear some good news,i feel so sick."
Queens Park Rangers defender Fitz Hall
"Please make Fabrice be ok, I'm praying for you bro."
Queens Park Rangers midfielder Shaun Wright-Phillips
"Please please let fab be ok! Honestly one of the nicest people in the world! Please everyone pray for him! Love you bro!!"
Norwich City striker James Vaughan
"This is now a day when football across the World comes together to pray for Muamba. puts everything into perspective."
Everton midfielder Tim Cahill
"Our thoughts and prayers are with Fabrice Muamba and his family right now. A wonderful person."
The English Football Association
"Heart goes out to Fabrice. Hope he's ok!"
Birmingham City defender Curtis Davies
"All my thoughts are with you Fabrice. Xx."
Former Manchester United defender Gary Neville
"Everyone connected with Wolves sends their thoughts and prayers to Fabrice Muamba, his family and all at Bolton Wanderers."
Wolverhampton Wanderers Football Club
"All our hearts with Fabrice Muamba, one of my closest friends at Bolton.. Im shocked, wishing him a fast recovery."
Wigan Athletic goalkeeper Ali Al Habsi
"Doesn't matter if you aren't a football fan Doesn't matter if you aren't religious RT this and Pray for Fabrice Muamba xxx."
West Ham United midfielder Ravel Morrison
"The thoughts of Blackpool Football Club are with Fabrice Muamba and his family."
Blackpool Football Club
"My hart goes out 2 Fabrice Muamba, his family and team mates at Bolton. Terrible what happened . Keep praying."
Manchester City midfielder Nigel De Jong
"My thoughts are with Fabrice Muamba's family. We all are praying for him and hope for a speedy recovery."
Tottenham Hotspur striker Emmanuel Adebayor
"Thoughts go out to muamba , I hope he's ok."
Wolverhampton Wanderers defender Jody Craddock
"Fabrice Muamba is one of the nicest and most respectful young men I have ever met in football. I'm thinking of you Fab get well soon. DG"
West Ham United co-owner David Gold
"My prays go out to Fabrice and his family may he have the strength to recover."
Former Arsenal and Manchester City midfielder Patrick Vieria
"Stoke City Football Club's thoughts and prayers are with Fabrice Muamba and his family at this time."
Stoke City Football Club
"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."
Tottenham Hotspur defender Kyle Walker
"Big up Fabrice Muamba. Wish him good and will pray alongside his family. Pls forget abt winning or losing. #LotOfLove."
Tottenham Hotspur striker Louis Saha
"Unbelievable what happened today!! Fabrice Muamba my thoughts are with you and your family. I will keep praying and hope you will be ok!!"
Liverpool striker Dirk Kuyt
Liam Apicella
