The midfielder is being linked with a Juventus move this season.
"It has been about two years now that (Giuseppe) Marotta and (Fabio) Paratici have been asking me about him and I must say that they have behaved impeccably," Cellino told Gazzetta dello Sport.
"They have never put pressure on us, and I appreciate that.
"If they were to ask again in January, I would leave Radja free to decide what happens.
"He has always given everything, maybe he deserves a new challenge. At Cagliari we appreciate the situation we are in."
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