The Argentine was first of the top seeds to lose in the men's draw this year, going down 6-3 6-3 6-7 3-6 6-3 to Chardy in the third round.
The Frenchman said: "If I wanted to win, I had to take my chances and go for it. Today, I was a little bit scared before I came on the court.
"I'm very happy when my form is like this against a good player like Juan Martin."
The world number 36 will face Andreas Seppi in the fourth round.