The England national team wrote on X: "We're extremely saddened by the passing of George Baldock. George was close to many of our players, and represented Greece – our opponents on Thursday night. We're thinking of George's family, friends and team-mates at club and country at this difficult time."
Meanwhile, MK Dons and Northampton Town, two other clubs Baldock represented, expressed their sadness at the news.
"We are deeply devastated and saddened to learn about the shocking news of former Academy graduate and MK Dons player, George Baldock," MK Dons wrote. "George started his career at Stadium MK, where he worked his way through the youth ranks and made his senior career debut at the Club before reaching the heights of the Premier League in later years.
"Everyone affiliated with MK Dons shares a great love for George, Sam and the Baldock family, and we would like to share our sincerest condolences during these awful times. You will always be one of our own, George."
Northampton added: "We are deeply saddened to learn of the passing of former loanee George Baldock at the tragically young age of 31. George made 5 appearances in 2011 on loan from MK Dons before playing for Oxford and Sheff Utd. Sending our sincerest condolences to George’s family/friends."