Iker Casillas' former club Real Madrid have led the messages of support to the goalkeeper after he suffered a heart attack in training with Porto.
The Portuguese club confirmed on Wednesday that Casillas had been taken to hospital, adding that he was in a stable condition after a heart problem had been "resolved".
Casillas won five LaLiga titles during his 16 seasons with Madrid, also celebrating a trio of Champions League successes before departing the club in July 2015.
The former Spain international was a World Cup winner in 2010, as well as triumphing at Euro 2008 and 2012, with Madrid wishing their former captain well.
"Real Madrid wishes to offer its full support to our beloved captain Iker Casillas," the club said in a statement.
"Iker Casillas has shown us how to overcome the most incredible challenges throughout his professional career, adding significantly to our club's successes.
"He's shown us that giving up has no place in our way of life and demonstrated time and again that staying strong during the hardest of challenges is the only path to victory.
"Real Madrid and all of madridismo look forward to seeing our legendary captain back in good health as soon as possible and we send him all the encouragement in the world."
Former Madrid team-mates Gareth Bale and Mesut Ozil were among the footballers to post messages of support to Casillas, who was widely regarded among the world's finest goalkeepers at his peak.
"Get well soon my friend," Wales international Bale wrote on Twitter, while Ozil said: "Best wishes to Porto! Hope all is going well. Get well soon Iker Casillas."