The ex-Italy international was diagnosed with pancreatic cancer five years ago, but was given the all-clear in 2020.
He then became a member of Roberto Mancini’s backroom staff as Italy won Euro 2020, but had to leave that role in December 2022 to focus on his health.
Although Gyan never played under him, the veteran striker has great respect for Vialli and what he did as a player and coach.
“We lost another giant. One of the best strikers of his generation. RIP legend” the former Ghana captain wrote on Twitter.
Vialli played for Sampdoria, Juventus and Chelsea, where he was a player-manager before being assigned permanently.
As Blues manager, he won the FA Cup, League Cup, Community Shield, UEFA Cup Winners’ Cup and UEFA Super Cup.
Meanwhile, Italian Football Federation (FIGC) president Gabriele Gravina has also paid tribute to Vialli.
“Gianluca was a wonderful person and he leaves a void that cannot be filled,” said in a statement.
“I hope until the end he can do another miracle. But I feel sure that what he did for Italian football and the blue shirt will not be forgotten.”
A minute’s silence in Vialli’s memory will be held before all football matches in Italy this weekend.