Kelly says Greaves was as good as the two of the current best footballers in the world Cristiano Ronaldo and Lionel Messi during his playing days.
Greaves is considered as one of the best footballers of all-time in the rich history of English football, having achieved this status between 1957 and 1971.
He started his career in Chelsea before moving to Tottenham Hotspur in 1961 after a short stint in the Serie A with AC Milan.
Greaves is Spurs' record goalscorer having netted 266 times in 379 games for the North London-based club.
He was also a member of England's World Cup-winning squad in 1966, and ended his international career with 44 goals in just 57 caps, making him the fourth top scorer for the Three Lions.
Kelly told talkSPORT: “This morning I racked my brains. With most great players, you can see what they are doing and he had that muscle and explosiveness of Cristiano Ronaldo, the unbelievable close control of Lionel Messi.
“I’m deliberately picking these players to compare him to. I couldn’t really see what Jimmy was doing in the same way, there was no one around who you could say ‘oh, he was like that’.
“I heard the word instinct used as well. He had an unerring instinct of where to be and what to do.
“He did the bare minimum of effort, but he was so skilled, he could get the ball on the outside or inside of his foot, not many headers, and he would just slide the ball where it needed to be to embarrass defenders and get it across the line.
“Most of the goals I saw Jimmy score were two touches. One to kill it, the other to put it over the line with a pass.
“He could run from the halfway line as well, because that was what was required. Somehow, he always knew what was required.
“I wish I could make a modern comparison, but I can’t.”
