Top-seeded Marin Cilic of Croatia will play Russian wild card Evgeny Donskoy in the semi-finals of the Kremlin Cup in Moscow.
Cilic, last year's US Open champion, swept past Russia's Andrei Kuznetsov 6-2 6-1 in less than an hour in their quarter-final.
"I'm very happy the way I played today. Very aggressive and I was hitting the ball very early," said Cilic, who is the reigning champion in Moscow.
Donskoy won an all-Russian quarter-final 6-3 6-2 against Teymuraz Gabashvili.
Second-seeded Roberto Bautista Agut of Spain reached the other semi-final with a 6-4 6-2 win over France's Lucas Pouille.
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He next faces German Philipp Kohlschreiber, who won 6-2 6-4 against Dutch player Robin Haase.
