The No. 1-ranked and No. 1-seeded Williams shut out 18th-seeded Carla Suarez Navarro of Spain, the first "double bagel" in a quarterfinal at Flushing Meadows since 1989, when 18-time major title winner Martina Navratilova did it to Manuela Maleeva.
"When you play against Serena," Suarez Navarro said, "you know these things can happen."
On the men's side, Andy Murray stumbled at the end of the first set, dropping four points in a row. He faltered for a fleeting moment at the end of the second set, too, missing a simple volley after his opponent's between-the-legs shot.
What truly mattered most in Murray's fourth-round match, of course, was the ultimate result, and the defending champion wound up beating 65th-ranked Denis Istomin of Uzbekistan 6-7 (5), 6-1, 6-4, 6-4.
The third-seeded Murray reached the quarterfinals at Flushing Meadows for the third consecutive year.
Now Murray will play No. 9 Stanislas Wawrinka.
P Wednesday, 10 a.m., 5 p.m.
TV • ESPN2