The 6-foot-6 Argentinian, the 2009 U.S. Open champion, had only dropped 13 games in two matches before facing Chardy -- the fewest number of all the men -- until his 6-3, 6-3, 6-7 (3), 3-6, 6-3 third-round defeat.
Chardy won the first two sets and, after del Potro rallied to level at two-all, got the crucial break in the eighth game of the fifth set and then held to clinch the match, closing with an ace.
The 36th-ranked Frenchman frustrated del Potro with a mix of drop shots, well-angled forehands and backhand slices, one of which sent del Potro running into the stands in the third set.
Del Potro had been tipped as an outside contender for the title in the absence of 11-time major winner Rafael Nadal, but his loss leaves only leaves three Grand Slam winners in the men's draw. Of those, Andy Murray advanced on Saturday, and Roger Federer was playing a night match. No. 1-ranked Novak Djokovic continued his run toward a third consecutive Australian Open title with a third-round win on Friday night.
"Of course, it's not a good result after I came back from two sets down, but Jeremy played really well in the fifth set," he said. "He was so calm to close the match in the end.
"Jeremy played so strong during four hours. He made a lot of winners with the forehand, very good slices. In the end, when he had the chance to break me, he did. He played better in the important moments and he took the chance to win the match."
Chardy had a win over No. 3-ranked Andy Murray at Cincinnati last year, but said the win over del Potro was a bigger personal achievement in the circumstances.
"Here it's something more because Australian Open, third round, I play a top player," he said. "It's a big win for me. And maybe the best of my career."
He will meet Andreas Seppi in the fourth round after the No. 21-seeded Italian beat No. 12 Marin Cilic.
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