ROME (AP) _ Roger Federer lost to Italian wild card Filippo Volandri 6-2, 6-4 Thursday in the third round of the Rome Masters, extending his title drought to four straight tournaments.

The top-ranked Federer last won at the Dubai Tennis Championships in March. He has since failed to win at Indian Wells, California; Key Biscayne, Florida; Monte Carlo, Monaco; and Rome.

It's the worst stretch of Federer's career since becoming No. 1 in Feb. 2004.

``I don't know what's wrong. I have to analyze it myself,'' Federer said. ``It was over too soon for me today.''

Rome is a key clay-court warmup for the French Open, which begins May 27, and Roland Garros is the only Grand Slam that Federer hasn't won.

``(I need to) get back on the practice courts instead of the match courts,'' Federer said.

Andy Roddick's run also came to a halt Thursday. The third-ranked American lost to Juan Ignacio Chela of Argentina 6-0, 6-4. Chela next will face sixth-seeded Fernando Gonzalez, who beat fellow Chilean Nicolas Massu 6-7 (4), 6-3, 6-4.

Federer dropped his serve twice in the first three games and quickly lost control of the first set. In the second set, Volandri broke to take a 2-1 lead when Federer made four errors.

On Volandri's first match point, Federer hit a forehand into the net.

``I was always running behind the score,'' Federer said. ``The crowd didn't affect me much because nothing happened. It's just a disappointing loss.''

Federer often missed routine baseline shots and his body language conveyed little will to compete.

He hit only two winners with his forehand, normally his best shot, and made 44 unforced errors to Volandri's 23.

Federer's ability is usually enough _ even on bad days.

``It happens a lot, but sometimes I get through them,'' he said.

Federer arrived in Rome more than a week before the tournament started to step up his clay-court training.

``I was the first player to arrive. My preparation was perfect,'' Federer said. ``But let's not forget that Filippo played well today. Give the guy credit.''

The 53rd-ranked Volandri also played well in his only previous meeting with Federer, losing a three-setter here in the 2003 quarter-finals.

Italy's top player beat 13th-seeded Richard Gasquet of France on Wednesday for his first win against a top-20 opponent this season.

Roddick wasn't able to dominate with his usually reliable serve, allowing the 23rd-ranked Chela to dictate play from the baseline.

``I served horribly today and that made the rest of it a little tough for me,'' Roddick said. ``First and foremost, though, he just played better than I did. It wasn't even close today.''

Roddick served only one ace, late in the second set, and dropped his serve four times. He saved two match points on his serve while trailing 5-3 in the second set, but Chela served out the match at love in the next game.

``Too little, too late,'' said Roddick, whose performance came in sharp contrast to his straight-set win over 2004 French Open champion Gaston Gaudio of Argentina on Wednesday.

Roddick had won six of seven previous meetings with Chela, but those all came on the American's preferred hard-court surface.

``Obviously he's a bit more comfortable here,'' Roddick said.

Roddick was playing his first tournament since injuring his hamstring in the Davis Cup last month. A stomach virus also slowed his preparation before flying to Europe.

``I'm not feeling in as good a shape as I should be,'' Roddick said.

Later, Rafael Nadal's 73-match winning streak on clay faced a test against 15th-seeded Mikhail Youzhny of Russia. Youzhny has beaten the Spaniard in their last two meetings _ both on hard courts.

Nadal went to a hospital for a checkup Thursday morning following a dizzy spell.

``It was the same as yesterday,'' Nadal's spokesman Benito Barbadillo said. ``He was just feeling a little dizzy, that's it.''

Nadal is aiming to become the first player to win the Rome tournament in three consecutive years. He beat Federer in a fifth-set tiebreaker in last year's final.