Kean has returned to the club after a successful loan spell at PSG last season, during which the Italian forward scored 13 goals in 26 league appearances.
There has been speculation surrounding the future of the 21-year-old, who still has three years remaining on his contract at the club.
Despite a move away this summer remaining a possibility, Nevin is of the view that Kean could still have a lot to offer at Goodison Park.
“I watched Moise Kean before he came to Everton, and I thought that was going to be one of the best pieces of business in the club’s history,” Nevin told TribalFootball.com (on behalf of British Gambler).
“He looked amazing before arriving, but it just hasn’t worked out for him so far.
“If Rafa can get the best out of him alongside Dominic Calvert-Lewin, then they will be quite an attacking force.”
It’s not only Kean who Nevin is excited to see in action, however.
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The 57-year-old has claimed that Gray could be the real difference-maker for the Toffees, following his summer switch from Bayer Leverkusen.
“Demarai Gray might be the big one, he is a stunning talent and there were times at Leicester where he looked like the next Riyad Mahrez,” said Nevin.
“If Rafa can get the best out of him and Moise Kean, then Everton will have a really good season.”