Kante reached 250 Chelsea appearances at the weekend.
"It has been 250 times a pure joy to watch him. Of course, it is pure joy and luck to be his coach because he is a fantastic guy and player," said Tuchel.
"He is so unique, and I don't know anybody that doesn't love him, even friends and family, friends who support other teams, they all love N'Golo Kante. There is a reason for this."
Tuchel also congratulated Mendy who last week qualified for the World Cup with Senegal for the second successive tournament.
"A winner of the African Cup of Nations and now in the rematch of the final against Egypt he made it again through penalties and won again, to join the World Cup with his country," the German added.
"I think it is a strong team and I think they deserve it; he deserves it. A brilliant 18 months and he will arrive with a competitive team for Qatar."