WASHINGTON (AP) -- Fourth-seeded Tommy Haas beat Leonard Mayer 6-4, 7-5 to set up a quarterfinal with fellow German Tobias Kamke at the Citi Open Wednesday. Kamke beat Marinko Matosevic 6-4, 6-3.
"I'm pretty pleased with the way I played the big points and the position I put myself into,'' Haas said.
It will be the first time Haas and Kamke have played each other.
"It should be quite interesting,'' Haas said. "It's always tough when you play someone for the first time, to figure out how they play or what they do like and what they don't like, but I look forward to it.''
In other men's action, second-seeded Alexandr Dolgopolov beat Rueben Ramirez Hidalgo 6-1, 6-3, and James Blake advanced with a 6-2, 6-4 victory over qualifier Marco Chiudinelli. Blake didn't lose a break point in the match.
"Anytime you do that, it's a pretty darn good feeling,'' Blake said. "Right from start to finish I felt good.''
On the women's side, Coco Vandeweghe, seeded for the first time on the WTA Tour, brushed off the notion that she was under added pressure.
In fact, she barely even knew she was seeded before the Citi Open started.
"I didn't know I was seeded until I got the schedule and saw there was a seven next to my name,'' Vandeweghe said. "I don't look at the draw, but I thought it was pretty cool to be seeded.''
Vandeweghe topped qualifier Aravane Rezai 6-2, 6-2 to advance to the quarterfinals Tuesday. She'll meet No. 4 Vania King, who beat Irina Falconi 6-2, 7-6 (5), in an all-American quarterfinal.
Vandeweghe made her first WTA Tour final in Stanford last month, where she lost to Serena Williams. Truth be told, she'd rather not be in Washington this week - her dream would put her in London, playing in the Olympics - but she's hoping to build on her recent success.
"That's a dream of mine to compete in the Olympics and win a medal eventually. It's almost more of a goal for me than to win a Grand Slam, because my mom was in the Olympics,'' said Vandeweghe. Her mother, Tauna Vandeweghe, is a former Olympic swimmer. "But I'm out here to play in this tournament and to win this tournament.''
King was up 6-5 in the second set and had a chance to win with Falconi serving, but hit a shot wide on match point, then again on the next point and Falconi pulled out the game.
"I wasn't calm enough. Obviously I was nervous,'' King said. "I kind of second-guessed myself.''
On the final match point in the tiebreaker, Falconi hit a shot wide to give King the victory.
"I know every match I win will boost my confidence and help my game,'' King said. "I feel like my game is there, I just need to play more matches and get used to the competition.''
Four seeded players have already been knocked out of the women's draw. The latest to go was eighth-seeded Olga Govortsova, who was beaten by 18-year-old Eugenie Bouchard 1-6, 6-0, 6-3. The win put Bouchard in her first career WTA Tour quarterfinal.
Qualifier Jana Cepelova also advanced to her first quarterfinal, beating Edina Gallovits-Hall 6-3, 6-4, and Magdalena Rybarikova topped Eleni Danilidou 6-3, 7-5.
Top-seeded Anastasia Pavlyuchenkova avoided an upset with a 6-2, 2-6, 6-3 victory over Melinda Czink.
Along with King and Vandeweghe, who will play Thursday, third-seeded Sloane Stephens advanced Tuesday to put three Americans in the quarterfinals. Stephens will face Eugenie Bouchard in Thursday's last match on the stadium court.
"I think it's great that we're all in the quarters,'' Vandeweghe said. "It's great to have all these Americans inside the top 100. With all the talk about, 'No good Americans coming up,' we've got a lot of young girls and I think we're all doing well individually and doing different things very well.''