Moscow, Russia -- (Sports Network) - Former world No. 1 Marat Safin upended fellow Russian Nikolay Davydenko in Friday's quarterfinals at the $1.049 million ATP Kremlin Cup.

The seventh-seeded Safin improved to 3-4 lifetime against the top-seeded and two-time defending champion Davydenko by prevailing 7-6 (7-5), 4-6, 6-4 on the indoor carpet at Olympic Stadium. Davydenko had won this event three of the last four years and beat France's Paul-Henri Mathieu in last year's finale.

Davydenko, who is still a stellar 17-3 at this tournament, beat Safin in the title bout here two years ago.

Another Day-5 upset came when Fabrice Santoro toppled his fourth-seeded fellow Frenchman Mathieu 6-3, 2-0, as Mathieu retired due to an illness. Mathieu was a runner-up in Metz, France last week, was the runner-up in Moscow last year, and captured this event back in 2002.

In other quarterfinal play, Russian Igor Kunitsyn cut down France's Jeremy Chardy 6-4, 6-2 and German Mischa Zverev outlasted Serbian Viktor Troicki 6-4, 3-6, 7-5 by saving a pair of match points.

Saturday's semifinals will pit Safin against Zverev and Santoro versus Kunitsyn.

The 2008 Moscow champ will collect $171,000.