(CNN) -- Novak Djokovic's hopes of matching Rafael Nadal on clay were dashed by unheralded German Philipp Kohlschreiber at the French Open on Saturday.
Novak Djokovic had been seeking to go better than his semifinal defeats in the past two years.
The fourth-ranked Serbian became the highest-profile casualty of the men's draw so far as he crashed out in straight sets in the third-round match on Court One at Roland Garros.
Djokovic reached the semi-finals in Paris for the past two years, and had high hopes of again testing Nadal after going close to besting the world No. 1 in the last four at Madrid two weeks ago.
But he proved no match for 29th seed Kohlschreiber, who won 6-4 6-4 6-4 against a player who has this year lost his No. 3 ranking to Andy Murray but won on clay in Belgrade and reached finals in Monte Carlo and Rome.
"I was disappointed with the way I was performing. I couldn't find the rhythm throughout the whole match," Djokovic said. "I was trying to find the comfort zone but my legs were really stuck.
"I was trying not to be frustrated with my unforced errors and trying to stay positive and wait for my chances, but he didn't give me any. He played tactically really smart and I had no solutions.
"As I said before, the opening rounds are very dangerous because the players are lower ranked and they have nothing to lose."
Kohlschreiber, who had never got past round two at Roland Garros before and who has yet to reach a Grand Slam quarterfinal, will next play Spanish 16th seed Tommy Robredo.
Robredo progressed with a 4-6 7-5 6-1 6-0 win against unseeded Argentine Maximo Gonzalez.
World No. 2 Roger Federer showed frailty against lesser opposition for the second match in a row, but progressed into the fourth round with a 4-6 6-1 6-4 6-4 win against 32nd seed Paul-Henri Mathieu.
The Swiss, who has lost the past three finals to Nadal, will next play unseeded German Tommy Haas, who earlier beat Frenchman Jeremy Chardy 7-5 6-3 4-6 6-4.
Earlier on Saturday, American sixth seed Andy Roddick reached the fourth round of the event for the first time in his career with a 6-1 6-4 6-4 victory against unseeded Frenchman Marc Gicquel.
The 26-year-old will face another home favorite in Gael Monfils, with the 11th seed having defeated Austrian 24th seed Jurgen Melzer 6-2 4-6 6-3 6-1.
France have another player in the last 16 as ninth seed Jo-Wilfried Tsonga progressed with a 6-2 6-2 6-2 crushing of Belgium's Christophe Rochus.
Tsonga, losing finalist at the 2008 Australian Open, will take on fifth seed Juan Martin Del Potro following the Argentine's 6-4 7-5 6-4 win against Russian 25th seed Igor Andreev.