The France midfielder, signed in the summer from Lyon, has been earmarked by City management as Kevin de Bruyne's successor.
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Viana says City chiefs have no doubt about Cherki's ability, but this season will be one of adaption.
He said, "He's an extraordinary player, but he still has to adapt to a very demanding league.
"This season will be crucial for his development. He has all the qualities to become a key player and gradually replace key players like (Ilkay) Gundogan and (Kevin) De Bruyne."