Second-seeded John Isner has defeated Canada's Vasek Pospisil in straight sets in the big-serving American's opening match at the Atlanta Open.
Coming off a victory on Sunday in the Hall of Fame Open in Newport, Rhode Island, Isner won 6-3 6-4 as he seeks his fourth Atlanta title in five seasons.
He lost to Nick Kyrgios in the final last year.
Isner set up a quarter-final at Atlantic Station against Slovakia's Lukas Lacko, a 6-3 6-1 winner over sixth-seeded Donald Young.
Third-seeded Gilles Muller of Luxembourg and Tommy Paul also reached the quarter-finals.
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Muller beat France's Quentin Halys 6-4 6-7 (1) 6-3, and Paul topped Tunisia's Malek Jaziri 6-7 (5) 6-4 6-3.
In the top half of the draw, top-seeded Jack Sock will open play Thursday with a second-round match against Israel's Dudi Sela while Australia's John Millman plays American Ryan Harrison.
