Viktor Troicki has crashed out at the last-16 stage of the Kremlin Cup after a three-set defeat to Daniil Medvedev in Moscow.
Russian Medvedev, the world No.123, battled back from a set down to earn a 3-6 6-3 6-1 win, rounding off the victory in style by winning five straight games.
He will face France's Stephane Robert for a place in the semi-finals.
Germany's Philipp Kohlschreiber progressed to the quarter-finals following a 7-5 3-6 6-3 success over Serbia's Dusan Lajovic in two hours and 16 minutes.
Andrey Kuznetsov was unable to make it two Russians into the last eight after falling to a 6-3 3-6 6-3 defeat at the hands of Brazil's Thomaz Bellucci.
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In the Stockholm Open, second seed Grigor Dimitrov eased into the quarter-finals with a 6-3 6-2 victory over Estonia's Jurgen Zopp.
The Bulgarian broke Zopp's serve three times in the match as he continues his good recent form and will take on Kevin Anderson for a place in the semi-finals.
The 30-year-old South African battled past Ryan Harrison of the United States with a 7-6 (10/8) 6-4 success to earn his place in the last eight.
Juan Martin Del Potro beat Nicolas Almagro of Spain in straight sets to make the quarter-finals, while Tobias Kamke also progressed with a win over Moldova's Radu Albot.
Elsewhere, Gilles Simon bowed out of the European Open in Antwerp following a 6-4 6-4 defeat to Jan-Lennard Struff.
Diego Schwartzman reached the quarter-finals with a 6-4 6-4 win against young American Taylor Fritz, while Romania's Marius Copil also progressed with a 7-6 (7-3) 6-2 success over Belgium's Steve Darcis.
