Kante has enjoyed a superb season for Chelsea since arriving from champions Leicester last summer - with his ability to protect the Blues' defence, create attacks and even score goals playing a key role in Antonio Conte's side sitting top of the standings.
Koscielny was full of praise for Kante, who he plays with in the France national team, last summer following his impressive debut season in England at Leicester.
And after seeing how Kante has adapted to life at Chelsea, Koscielny believes the Blues midfielder is now the best player in the entire top flight.
"He's the best player in the league, simple," Koscielny said during a France press conference on Thursday.
"He has this ability to adapt. He has made tremendous progress.
"When you have a player like that in the middle [of the pitch]... He knows what he can do and not do.
"He does it admirably."