MASON, Ohio -- Defending champion Roger Federer reached the third round of the Western & Southern Open with a 6-3, 7-5 win Tuesday over Argentina's Juan Martin del Potro, who had won the last two matches between the two, including the 2009 U.S. Open final.
"I expected a tougher match, for obvious reasons," he said. "It went better than I thought. I had a wonderful first set, and the second set, too. I was able to keep him from playing the game he likes to play. I was able to mix it up and serve well."
Earlier, unseeded Andrey Golubev of Kazakhstan upset Federer's countryman, 16th-seeded Stanislas Wawrinka, 3-6, 6-4, 6-1 in the first round.
Golubev ended a losing streak of 18 consecutive matches in ATP play.
"It was very important," he said. "I lost a few matches when I was one or two points away from victory. It's really tough to digest."
Eight-seeded Tomas Berdych of the Czech Republic became the first man to advance to the third round. Berdych defeated Argentina's Juan Monaco 7-6 (2), 6-0. Ninth-seeded Nicolas Almagro, 10th-seeded Gilles Simon of France and No. 15 seed Jo-Wilfried Tsonga, a Wimbledon semifinalist, also moved on.
Croatia's Ivo Karlovic enjoyed a 19-1 advantage in aces while rolling to a 6-1, 6-3 victory over Germany's Florian Mayer.
Russian Nikolay Davydenko beat Ukrainian Sergiy Stakhovsky 6-2, 7-6 (5). Serb Janko Tipsarevic, ranked No. 20, ousted Frenchman Edouard Roger-Vasselin 6-0, 3-6, 7-6 (5); and Croat Ivan Dodig defeated Latvian qualifier Ernests Gulbis 6-3, 7-6 (3).
Information from The Associated Press was used in this report.