Players, managers and officials have expressed their support for Bolton's Fabrice Muamba, who is critically ill after collapsing on Saturday.
The midfielder, 23, suffered a cardiac arrest during the FA Cup quarter-final tie at Tottenham.
Arsenal's Johan Djourou, a former team-mate of Muamba, posted on Twitter that he had visited his friend in hospital.
"Love you so much man! Keep fighting. Everybody please pray for him he's an amazing man and friend," he tweeted.
Muamba was taken to the London Chest Hospital after falling to the pitch at White Hart Lane, with the match subsequently abandoned after referee Howard Webb called visibly distressed players off the field.
Both sets of fans chanted Muamba's name as he was taken off the pitch on a stretcher, while on Sunday there was applause for the player before the Premier League match between Wolves and Manchester United at Molineux.
Former Bolton defender Gary Cahill scored the opening goal in Chelsea's FA Cup quarter-final against Leicester on Sunday and revealed a T-shirt with the message: "Pray 4 Muamba".
Afterwards he said: "Today's match was like a blur and I just hope he's alright. My mind was in a different place."
Since the incident, there have been many messages of support for the former Birmingham player.
Spurs' Rafael van der Vaart, who was one of those on the pitch when Muamba collapsed, tweeted: "Terrible what happened with Muamba during the game. We're all praying for him."
England international Jack Wilshere who played with Muamba at Bolton, wrote: "I will never forget my first day [at Bolton]. Fab showed me around and basically looked after me. If you know him then you will know what type of man he is! A leader and a genuinely nice guy! Everyone keep praying."
Middlesbrough defender Justin Hoyte, who played in the Arsenal youth team with Muamba, posted: "I seriously hope my best friend in football is OK. Stay strong bro, please please stay strong. God is with you remember that."
Arsenal, Muamba's first club, released a statement saying: "The thoughts and prayers of his many friends at Arsenal Football Club are with Fabrice and his family at this time."
And a spokesman from Muamba's former club Birmingham said: "The thoughts of everyone at the club are with Fabrice and his family.
"He was a very popular member of the club during his time here and everyone at St Andrew's is shocked and saddened to see what happened."
Former Blues chairman David Gold tweeted: "Fabrice Muamba is one of the nicest and most respectful young men I ever met in football. I'm thinking of you Fab, get well soon."
Manchester United manager Sir Alex Ferguson, after his team's 5-0 win at Wolves, said Muamba's situation puts "everything into perspective".
"What was terrific was that both sets of fans acknowledged there was problem," he added.
"The medical staff for both teams were fantastic, they got there immediately."
Support for Muamba extended overseas, with Italy and Juventus star Andrea Pirlo saying Juve's 5-0 win over Fiorentina was for his fellow midfielder.
"We want to dedicate our goals to Muamba, the Bolton player who fell ill on the pitch. We all support him," said Pirlo after the game on Saturday night.
Fifa president Sepp Blatter said on Twitter: "Shocked to hear about Fabrice Muamba. My thoughts are with him and his family, his club & loved ones at this difficult time."
Bolton's next scheduled match, against Aston Villa on Tuesday, has been postponed. Villa boss Alex McLeish also worked with Muamba at Birmingham.
"He is a manager's dream in terms of his commitment to the team," said McLeish. "I pray that Fabrice is able to pull through."
Norwich manager Paul Lambert understands what Muamba's friends and family are experiencing as he knew Phil O'Donnell, who died after collapsing on the pitch while playing for Motherwell in 2007.
He said: "It was horrific. Hopefully that lad is going to be OK.
"It happened up in Scotland a few years ago to a good friend of my own, so I know what people are going through but hopefully, he is going to pull through."