Top seed Roger Federer failed to find his true rhythm in his sluggish second round victory over wildcard Potito Starace at the Rome Masters on Wednesday.
The world number one made 35 unforced errors - 26 in the second set - before eventually shaking off the stubborn Italian 6-3, 7-6 (7/2).
Federer, who has reached the final of the last five ATP Masters Series events in which he has played and won four of them, said he felt he was playing the crowd as well as Starace.
"I knew being up against an Italian here in Rome was going to be difficult," said the 24-year-old Swiss.
"I had it here against Filippo Volandri and Andrea Gaudenzi, so I knew what to expect.
"The match was close, and I'm very happy to get through. He's a good clay player."
Still missing the French Open from his Grand Slam collection, Federer, who has never won the Rome title, next faces either Czech 14th seed Radek Stepanek or Finland's Jarkko Nieminen.
In-form Argentine fourth seed David Nalbandian swept into round three after beating Frenchman Paul-Henri Mathieu.
Nalbandian, 24, whose triumph in Estoril last week was his first ATP title of the year and elevated him to third in the world rankings, won 6-2, 6-4.
He next plays Spain's Alberto Martin, who defeated German 13th seed Nicolas Kiefer.
Nalbandian, beaten by Carlos Moya in the 2004 final here, feels his current form bodes well for Roland Garros, which starts later this month.
"The French Open is always special and I think I can be one of the guys fighting for the title, that's for sure," he said.
American Andy Roddick reached the last 16 by beating Australian Open runner-up Marcos Baghdatis.
Roddick, who lost to the 20-year-old Cypriot in the fourth round in Australia, gained revenge with a 3-6, 6-1, 6-2 victory.
Roddick admitted he performed way below his best in an error-strewn match.
"It's satisfying to get through because I served terribly for almost two sets," said the fifth seed.
Roddick's next challenger is Great Britain's Greg Rusedski, who beat Italy's Stefano Galvani.
Roddick insisted Rusedski would provide a stiff challenge.
"He beat Tommy Robredo on clay (in the first round) and that's no easy task," he said.
Gael Monfils upset American 16th seed Robby Ginepri to set up an all-French last 16 clash against veteran Fabrice Santoro.