The 22-year-old has been linked with a move to Arsenal in recent months after impressing last season for the Ligue 1 side.
“We never wanted to sell him, he is our captain and a major player for us,” said Comolli.
“He’s done well for us last season but we convinced him to stay.
“But I’m not being naive, I know it will be difficult to keep him and know he will end up in England or one of the top clubs in Europe.
“Whoever comes for him, it will cost them a lot of money.”