Roger Federer's [ Images ] dreams of winning his first Rome Masters title were shattered when he slumped to a 6-2, 6-4 defeat against Italian wildcard Filippo Volandri in the third round on Thursday.

Third seed Andy Roddick [ Images ] followed the world number one out of the claycourt tournament, losing 6-0, 6-4 to Juan Ignacio Chela, but defending champion Rafael Nadal [ Images ] remained on course for a hat-trick of Rome titles.

The Spaniard appeared to have overcome the dizzy spells that troubled him in the previous round and was back on form with a 6-2, 6-2 win over 15th seed Mikhail Youzhny.

Fourth seed Nikolay Davydenko [ Images ] also reached the quarter-finals with a 4-6, 6-2, 7-5 win over Italy's [ Images ] Potito Starace.

Federer, runner-up in Rome in 2003 and 2006, barely resembled the player who battled with Nadal in last year's thrilling five-set, five-hour final as he made 44 unforced errors to hand Volandri victory.

The defeat means the Swiss has gone four tournaments without a title -- his longest stretch since becoming world number one in February 2004.

"It's disappointing but there's nothing you can do about it. That's knock-out tennis," said a downcast Federer, denying he was ill or injured and dismissing the heat on Rome's centre court as a contributing factor to his defeat.

"I played good in my first match (to beat Nicolas Almagro), and usually after the first game I play better and better but today was the opposite.

"On clay you need to be solid and I wasn't. I don't know if you can say I was playing shockingly but I was making a lot of mistakes, serving badly -- giving him second serves all the time.

"It sometimes happens but usually I get through. And Volandri played well. Everyone is talking about how I played, but he already played well against (13th seed Richard) Gasquet (in the previous round).

"I know his game. I played a tough match against him here a few years ago, I played him in the juniors, so I know how tough he can be."

NEAR-PERFECT MATCH

Nadal showed few signs of vulnerability as he extended his winning streak on clay to 74 matches.

The 20-year-old Spaniard had undergone medical checks after suffering a dizzy spell during Wednesday's second-round win over Daniele Bracciali, but seemed his usual bustling self as he swept Youzhny aside with the minimum of fuss.

"I played a near-perfect match today," said Nadal, whose next opponent, fifth seed Novak Djokovic [ Images ], beat Marcos Baghdatis [ Images ] 6-2, 7-5.

Asked whether Federer's exit had cleared his way to equal Thomas Muster's professional era record of three Rome titles, Nadal replied: "No. I don't think so. There are still some very difficult matches to come, starting with the game against Djokovic."

Roddick's defeat came as little surprise. The big-serving American, who was playing his first tournament since a hamstring injury forced him to pull out of the Miami [ Images ] Masters in March, was no match for claycourt specialist Chela.

"I served horribly today and that made the rest of it a little tough for me," said Roddick.

"I actually started hitting the ball a little better in the second set and that allowed me to get in a little bit more. But I dug a good hole for myself in the first 10 minutes out there today."

In the quarter-finals Chela will play sixth seed Fernando Gonzalez [ Images ], who beat Nicolas Massu [ Images ] 6-7, 6-3, 6-4.