Washington: Japan`s Kei Nishikori, last year`s US Open runner-up, advanced to the semi-finals of the ATP and WTA Washington Open by beating Australia`s Sam Groth 6-4, 6-4 on Friday.
Fifth-ranked Nishikori, the top remaining seed after Britain`s Andy Murray crashed out in his opening match, booked a Saturday semi-final meeting with the winner of a later match between reigning US Open champion Marin Cilic, the third seed from Croatia, and German teen Alexander Zverev.
Nishikori seeks his third title of the year after Memphis and Barcelona and the 10th of his career. The 25-year-old Asian number one has reached his seventh ATP smei-final of the year.
On the women`s side, Australian second seed Samantha Stosur advanced to the semi-finals when Romania`s Monica Niculescu retired after losing the first four games.
Nishikori took advantage of his fifth break chance of the seventh game, taking a 4-3 lead when the Aussie hit a forehand drop volley wide, and held twice more to take the first set in 39 minutes.
Groth, ranked a career-best 62nd this week, denied Nishikori on three break points to hold in the opening game of the second set, but Groth`s fourth double fault of the match later gifted Nishikori a break for a 3-2 edge.
Nishikori denied Groth on two break points in the eighth game, holding for a 5-3 lead, and held at love in the final game to conclude matters after 86 minutes.
Groth, whose only ATP semi-final was last year at Newport, fired 15 aces but fell to 0-4 against top-10 foes in dropping his first meeting with Nishikori.
Eighth-ranked Cilic, the first reigning US Open champion at the US capital event since Andre Agassi in 2000, seeks only his second semi-final of the year, matching a run on Stuttgart grass.
Zverev, 18, is the youngest player in the top 100 and set to rise from 96th in the world. He`s Washington`s youngest last-eight player since Andy Roddick at 17 in 2000. No teen has won an ATP crown since Cilic at New Haven in 2008.
Other later quarter-finals at the US Open hardcourt warm-up event send US eighth seed John Isner against Lithuania`s Ricardas Berankis and Jack Sock against Steve Johnson in Washington`s first all-US quarter-final since 2003.