Jack Sock will meet top seed John Isner in the semi-finals of the US Men's Clay Court Championship after wins over Marcos Baghdatis and Hyeon Chung respectively.
Defending champion Sock was too good for Baghdatis, getting past his Cypriot opponent 6-4 6-4 in just over one hour, 21 minutes.
Sock won 93 per cent of points on his first serve, while he was far more clinical than Baghdatis with his return.
Seventh seed Baghdatis won just seven per cent of points from Sock's first serve as the American broke twice to complete the straight-sets win in Houston.
Meanwhile, Isner managed to save seven out of Chung's seven break-point opportunities in a 7-6 (7-5) 6-4 win.
The American only needed one chance to break his South Korean opponent and make the last-four for the first time since 2013, where he went on to defeat Nicolas Almagro in the final.
Isner and Sock have met four times in their careers, with four wins to the former and two to the latter. Isner also holds the advantage on clay, winning both times against Sock.
The other semi-final will be contested between Feliciano Lopez and Juan Monaco after they knocked out American duo Tim Smyczek and Sam Querrey respectively.
Lopez breezed past Smyczek 6-2 6-3 in one hour, 10 minutes while Monaco was hardly troubled by last year's runner-up Querrey in a 6-4 6-4 win.
Spaniard Lopez, the third seed, has the better record against Monaco, winning the past three meetings between the two.