World No. 68 Igor Sijsling of the Netherlands ousted German qualifier Michael Berrer in the first round of the Kremlin Cup on Tuesday.
Berrer, ranked 129 in the world, made Sijsling sweat for the first set to but couldn't maintain the pressure for a 7-6(7), 6-3 defeat.
In round two, the 25-year-old Dutchman will have a tougher opponent in second seed Andreas Seppi of Italy.
Seppi had a first-round bye. This will be the first encounter between the two players.
Earlier Tuesday, Russia's Konstantin Kravchuk defeated Evgeny Korolev of Kazakhstan 6-4, 6-3 in a battle of two qualifiers.
Kravchuk plays eighth seed Tatsuma Ito of Japan in the second round.