Davide Astori's former clubs AC Milan and Cagliari were joined by Italy great Franco Baresi and former Roma coach Rudi Garcia in paying tribute to the late Fiorentina player.
Astori was found dead in his hotel room on Sunday, prompting the postponement of his team's match away to Udinese and all of the day's other Serie A fixtures.
Capped 14 times by Italy at full international level, the defender was a product of Milan's youth system, the Rossoneri expressing their condolences to Astori's family and his Viola team-mates.
"A man who loved football and who grew up as footballer with us," the club said in a message posted on Twitter.
"AC Milan are shocked by the passing of Davide Astori. It is with great sadness that we offer our deepest condolences to his family and close ones and to ACF Fiorentina."
Former Milan captain Franco Baresi said he was "speechless" at the tragedy, adding: "I saw you grow up and [was] proud of the path you were taking."
A move to Cagliari in 2008 saw Astori make his first Serie A appearance and he remained a popular figure with the Rossoblu.
Cagliari tweeted: "With our shirt you have made your dreams come true, you scored in the national team, you were our brave captain, you made yourself loved by our people and you loved our land. Goodbye, Davide."
Roma, where Astori spent the 2014-15 season on loan, said: "AS Roma joins the pain of the world of football for the passing of David Astori. Shocked by the tragic news, managers, footballers and all the company's employees [share] the pain of his family."
Roma's sporting director Monchi reflected on a tragic experience during his time at Sevilla.
The club's Spain international Antonio Puerta passed away in 2007 after suffering a cardiac arrest playing against Getafe in LaLiga.
"I know the suffering, I know how it feels, I know the pain because unfortunately I have lived… with the ill-fated Antonio Puerta," he wrote.
"Much encouragement to his family, his friends and companions, the Fiorentina and all the Italian football."
Former Roma coach Rudi Garcia said: "The news of the premature death of my former player Davide Astori grieves me. Professional and exemplary boy... Rest in peace David."
The Italian Football Federation (FIGC) said its thoughts "are with the directors, coaches and staff who knew and respected Davide throughout Italian football, while we also offer our most profound condolences to the Astori family."
