Querrey is the sixth seed in a tournament filled with upsets and defections.
He defeated Nieminen 4-6, 7-6 (7-4), 7-6 (12-10) and will now face unseeded Ricards Berankis in the quarterfinals. Berankis was a 6-3, 6-3 winner over Roberto Bautista Agut.
Gael Monfils also made it to the quarterfinals by eliminating No. 4 seed Tommy Robredo 7-6 (7-2), 4-6, 6-2. Seventh-seeded Fernando Verdasco awaits Monfils in the quarters after defeating Robin Haase 6-4, 6-7 (8-10), 6-3.
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