Seven of the Top 8 seeds reached the quarterfinals at the Washington D.C. event led by Americans John Isner, Steve Johnson, Jack Sock and Sam Querrey.
Isner took the first set from Marcos Baghdatis in a tiebreaker, then rolled in the second for a 7-6(3), 6-2 win.
Isner will now meet fellow American Johnson who stopped the mini-run of Ryan Harrison 6-4, 6-4.
Second seed Gael Monfils cruised past Croatian Davis Cup hero Borna Coric 6-2, 6-3. The Frenchman who’s returning from injury has lost just 10 games in two matches. He’ll now face the Wimbledon quarterfinalist Querrey after Sam knocked out Alexandr Dolgopolov 7-6(5), 6-3.
19-year-old Alexander Zverev struggled by survived a test from Malek Jaziri 6-2, 5-7, 6-2. He’ll meet Frenchman Benoit Paire.
And Sock will meet big man Ivo Karlovic. Sock eased past Dan Evans while Karlovic ousted Bernard Tomic 7-6(4), 6-3.
“I was getting good stats on my serve; he didn’t have any chance there. In the second set, he hit one double-fault and I followed it up with good returns to get the break,” said Karlovic.
In Umag, with top seed Pablo Cuevas out, No. 2 Joao Sousa, Fabio Fognini and Jeremy Chardy headline quarterfinal action.
Top seed Feliciano Lopez collides with youngster Elias Ymer in the match of the day in Gstaad.
WASHINGTON FRIDAY SCHEDULE
STADIUM start 1:00 pm
ATP –  I. Karlovic (CRO) vs  J. Sock (USA)
Not Before 3:00 pm
ATP –  J. Isner (USA) vs  S. Johnson (USA)
ATP –  S. Querrey (USA) vs  G. Monfils (FRA)
ATP –  [WC] A. Zverev (GER) vs  B. Paire (FRA)
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