US Open Day 8

Published 2158 GMT (0558 HKT) September 5, 2016
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Juan Martin del Potro, pictured, faced Dominic Thiem in the fourth round of the US Open on Monday. Al Bello/Getty Images North America/Getty Images
And when the injury hit del Potro called for the trainer after three games, things looked bleak for the 2009 winner. KENA BETANCUR/AFP/AFP/Getty Images
But del Potro appeared unaffected while French Open semifinalist Thiem subsequently injured his knee. EDUARDO MUNOZ ALVAREZ/AFP/AFP/Getty Images
Thiem had to retire trailing 6-3 3-2 and del Potro was into his first grand slam quarterfinal since 2013. Mike Hewitt/Getty Images North America/Getty Images
He next faces Stan Wawrinka. The twice grand slam winner -- who saved a match point in the third round -- defeated Illya Marchenko 6-4 6-1 6-7 (5-7) 6-3. TIMOTHY A. CLARY/AFP/AFP/Getty Images
Elsewhere, Karolina Pliskova saved a match point to beat Venus Williams 4-6 6-4 7-6 (7-3) to make a first major quarterfinal. EDUARDO MUNOZ ALVAREZ/AFP/AFP/Getty Images
Williams, who won the last of her seven majors in 2008, held the match point at 5-4 in the third on the Pliskova serve. Pliskova saved it with a gutsy swinging volley. EDUARDO MUNOZ ALVAREZ/AFP/AFP/Getty Images
But there were no issues for her younger sister, Serena. The top seed crushed Yaroslava Shvedova 6-2 6-3 to record a leading 308th grand slam win. EDUARDO MUNOZ ALVAREZ/AFP/AFP/Getty Images