The 21-year-old has been linked with Manchester United, Real Madrid, Bayern Munich and Arsenal after an impressive 2019-20 campaign for Champions League semi-finalists Leipzig.
He recently admitted to talking to other clubs despite appearing to end speculation over his future by signing a new three-year deal with the Bundesliga side at the end of July.
And Nagelsmann concedes it may prove too difficult to keep hold of the highly rated centre-back – who scored for France on his second appearance on Tuesday – in next year’s window.
“He will be here for the season. I’m sure about that,” Nagelsmann told ESPN. “As for the future, I’m not sure as he is very talented.
“Lots of clubs will want to buy – perhaps next season it could be real that he leaves the club. But this season he will stay.”
Leipzig sold their all-time top scorer Timo Werner to Chelsea in June and have seen an array of other first-team stars linked with the exit after last season’s exploits.
However, Nagelsmann has no complaints about bigger teams pouncing for his players and says it is down to his club to continue developing more talent.
“It is normal when you work with young guys that clubs will try and find young talented guys in the transfer market,” he said.
“It is normal that bigger clubs will try and buy these players. You have to deal with that, you’ve got to be one step forward when you buy new players or find new players.
“Our scouting should be good and we have made a lot of good decisions in the transfer market.”
Leipzig finished third in the Bundesliga last season and begin their 2020-21 campaign with a home match against Mainz 05 on September 20.
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