World No. 124 Alex Bogomolov dumped Nikolay Davydenko out of the Kremlin Cup in the first round on Tuesday, scoring the first upset of a seed in the $740,000 tournament.
Fifth seed Davydenko is a three-time champion at his home event, winning in 2004, 2006 and 2007, but was unable to maintain a late comeback to go down 7-5, 6-4.
"I lost because I made 50 errors, who could you not lose if you make so many mistakes," the Russian No. 2 said after the game. "It was not Bogomolov who made me do them. I tried to attack, tried to play my game and that's why I made mistakes."
Bogomolov took the first set with a late break that he converted, before racing to a 4-0 lead in the second before the Ukrainian-born Davydenko pulled the scores back to 4-4.
But Muscovite Bogomolov fought back to claimed a famous victory and a round-two match with world No. 117 Ivo Karlovic of Croatia or Simone Bolelli of Italy.
After the game Bogomolov, 29, recollected their encounter in the China Open earlier this month when Davydenko won in two sets, stating he adjusted his style of play.
"I started to play higher and send more balls to the left side because in Beijing we almost played table tennis, very fast," he said. "We started like that today, so I started to play higher to have more time to return to the center."
Earlier Tuesday, seventh seed Carlos Berlocq had to dig deep to eliminate local wild card Andrey Kuznetsov in a three-set thriller 1-6, 6-4, 6-3.
And Igor Sijsling of the Netherlands ousted German qualifier Michael Berrer 7-6(7), 6-3.
Elsewhere, Russia's Konstantin Kravchuk defeated Evgeny Korolev of Kazakhstan 6-4, 6-3 in a battle of two qualifiers.