Djokovic has been suffering with the flu all week but was still able to defeat Roger Federer in a marathon three-hour tie yesterday.
But that match must have took its toll on his body as the Serbian lost 7-5, 6-4 to Khachanov this afternoon.
And Djokovic revealed after his loss that he was struggling with illness throughout the clash.
“I am very happy to come to the finals but I didn’t feel too good today,” Djokovic said.
“I would like to give a lot of respect to Karen for playing such fantastic match today and he deserves to win.
“There is lots of tradition in Paris and this is a great city.
“Thank you everybody for coming and supporting us.”
Meanwhile, Khachanov was delighted to win the biggest trophy of his career to date.
The Russian will climb up to No 11 in the world rankings next week and he is thrilled to end the season on such a high.
“It means the world to me. It is one of the biggest titles in my career so far,” he added.
“I couldn’t be happier to finish the season like this.
“To win the last tournament of the season – a Masters 1000.
“Against Novak Djokovic, the world No 1, that is the only explanation.
“I have the same goals as I have for this year, to finish as high as possible.
“I need to keep working with my team on my game, to keep improving day by day.
“I need to keep competing with guys like Novak on the biggest stage more consistently.”
Source : EXPRESS