Updated

Former top-five star Nikolay Davydenko upset fourth-seeded Swiss favorite Stanislas Wawrinka in a pair of tiebreaks Tuesday at the Swiss Indoors tennis event.

The Russian veteran Davydenko dismissed Wawrinka in 7-6 (9-7), 7-6 (7-3) fashion on the indoor hardcourts at St. Jakobshalle.

Another upset came when promising Bulgarian Grigor Dimitrov took out eighth- seeded Serb Viktor Troicki 6-3, 6-2, while sixth-seeded Russian Mikhail Youzhny avoided the upset bug by pasting Aussie Bernard Tomic 6-0, 6-2 on Day 2.

Meanwhile, American comeback kid Brian Baker took out qualifier and Czech veteran Radek Stepanek in come-from-behind fashion, 2-6, 7-6 (7-5), 6-3, and South African slugger Kevin Anderson topped Finn Jarkko Nieminen 7-6 (7-4), 6-3. Nieminen was a Basel runner-up in 2007.

Roger Federer's second-round opponent will be last week's Moscow runner-up Thomaz Bellucci of Brazil, who rallied to beat Japan's Go Soeda 4-6, 6-4, 6-3.

The Swiss icon Federer beat Japan's Kei Nishikori for a second straight and fifth overall Basel title a year ago. He also claimed championships here from 2006-08 and was a Swiss Indoors runner-up in 2000, 2001 and 2009.

Additional opening-round wins came for Aussie Matthew Ebden and Swiss wild card Marco Chiudinelli.

In a first-round affair on Wednesday, last week's Vienna champion, second- seeded Juan Martin del Potro of Argentina, will take on fellow South American Alejandro Falla of Colombia.

The 2012 winner of this $1.84 million event will earn $440,000.