Russia's Daniil Medvedev upset Bulgarian fourth seed Grigor Dimitrov 6-4, 6-2, firing eight aces and dropping only six points on his first serve in the 63-minute triumph, avenging a June quarter-final loss at Queen's in their only prior meeting.
Nishikori, victor of this tournament in 2015, prevailed 6-4, 7-5 in 1 hour, 49 minutes at the Rock Creek Park Tennis Center in Washington.
Nishikori, the 2015 Washington victor, beat three-time champion Juan Martin Del Potro 6-4, 7-5, for only his second victory in seven matches against the Argentine 13th seed. Anderson sealed the win on his second match point.
In the third set it really seemed like Thiem, the number one seed of the tournament, and seventh seed in the world, would win the match. "I just didn't get the feel of the serve".
"If you break Anderson twice in one set, you have to win it", Thiem said.
The third set tiebreaker is where things really became tense. "I felt I had a shot after winning the second set but got broken early in the third set and it's much harder to come back against a big server".
The quarterfinal matchups are Anderson vs. Bhambri, Raonic vs.
"I've practiced with him before but that was a few years ago".
Anderson didn't want to waste a challenge over the call though and Thiem would concede the point.
epa06125108 Jack Sock of the United States in action against Milos Raonic of Canada during their quarter-final match of the Citi Open Tennis Tournament at the Fitzgerald Tennis Center in Washington, DC, USA, 04 August 2017.