Robson said: "We've lost a great friend, a great chum and he was a maestro in footballing terms.
"It's distressing. It's a long time since I was so distressed about the death of anybody to be honest.
"I've seen a lot of great players but in that sense he was unsurpassed. He was a valued friend, a great colleague, great to play with and it's very sad. Very sad."