Former club Roma are interested in the midfielder, who is reportedly unhappy with the lack of action he has seen this season.
Zenga told Sky Italia: “Let's not forget that there are five substitutions and there are still many games to play.
“But if a player comes to me as a club and says he is not happy and wants to leave…
“Maybe someone who is unhappy doesn't even train at a high level and ends up lowering the overall standard.”
Roma have already had one swap offer involving Lorenzo Pellegrini rejected by Inter.
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