Four-time winner Roger Federer, three-time runner-up Novak Djokovic and reigning champion Andy Murray were among Wednesday's second-round winners at the $2.825 million Western & Southern Open.

Federer posted a 6-3, 6-2 victory over Russian Alex Bogomolov Jr. in his first action since losing to Murray in the gold medal match at the London Olympics. The world No. 1 Federer titled here in 2005, 2007, 2009 and 2010.

The second-seeded Djokovic got past Italian Andreas Seppi, 7-6 (7-4), 6-2. The reigning U.S. Open and Australian Open champion is fresh off his Masters title in Toronto last week.

Djokovic lost to the two-time champion Murray in last year's marquee finale in suburban Cincinnati and also suffered finals setbacks here in 2008 and 2009 to Murray and Federer, respectively.

Up next for Djokovic will be Russian veteran Nikolay Davydenko.

The third-seeded Olympic gold medalist Murray, meanwhile, mauled American wild card Sam Querrey 6-2, 6-4.

Murray will meet Frenchman Jeremy Chardy on Thursday.

Swiss Stanislas Wawrinka knocked off fourth-seeded Spaniard David Ferrer with a 6-4, 6-1 triumph.

Sixth-seeded Olympic bronze medalist and former U.S. Open champion Juan Martin del Potro reached the third round with a 7-5, 6-2 victory over resurgent German Tommy Haas. The Argentine del Potro will encounter Serb Viktor Troicki in the round of 16.

Spaniard Pablo Andujar advanced when seventh-seeded Serbian Janko Tipsarevic retired in the second set due to a virus. Andujar took the opening set 6-4 and was leading 4-1 at the time Tipsarevic called it quits.

Two-time Cincinnati runner-up Mardy Fish reached the third round with a 6-3, 6-1 victory over Argentine Carlos Berlocq, while 12th-seeded Croat Marin Cilic dismissed American qualifier Jesse Levine 7-5, 7-6 (8-6) on Day 4.

Up next for Fish will be tough Czech veteran Radek Stepanek, who took out eighth-seeded Argentine Juan Monaco 7-6 (7-2), 6-1.

Fourteenth-seeded rising Japanese Kei Nishikori overcame fading American wild card James Blake 2-6, 6-4, 6-4, while another rising star, Canadian slugger Milos Raonic, bested Cypriot Marcos Baghdatis 6-7 (6-8), 6-3, 6-4.

In other second-round action on the hardcourts at the Lindner Family Tennis Center, the former top-five star Davydenko drubbed German Florian Mayer 6-3, 6-3, the lucky-loser Chardy doused Uzbekistan's Denis Istomin 6-4, 6-3, and Troicki trounced former world No. 1 Aussie Lleyton Hewitt 6-2, 6-0. The wild card Hewitt was the Cincy runner-up in 2002 and 2004.

This seventh of nine ATP Masters tournaments will pay its 2012 champ $535,600.