Arsenal manager Arsene Wenger praised Pat Rice's "fighting spirit" after the Gunners great was diagnosed with cancer.
Former Arsenal captain Rice, 64, the London club's skipper when they won the FA Cup in 1979, made 528 appearances for the Gunners.
And the Northern Irishman later served as Wenger's assistant from the moment the Frenchman arrived at the club in 1996 until he retired at the end of last season.
"It is very sad news," Wenger told Arsenal's website on Friday. "Not only do we love him, but of course we are very grateful for what he has done here.
"We are in touch with him, but I trust his legendary strength to get over it.
"I am confident that he still has the fighting spirit he always had to get over it and that he will come out in a successful way."
Wenger added: "That is what he needs now (strength of character) - he has that. In such a difficult period, it is a huge resource.
"His mental state is very determined, very strong as he always has been.
"He will fight for that, I have complete trust that he will come out in a very strong way and of course let us hope for the best."