Martin Klizan inflicted a semifinal defeat on Stan Wawrinka in St. Petersburg and will take on top seed Dominic Thiem in the final.
US Open champion Naomi Osaka and Karolina Pliskova will meet in the Tokyo Open final.
Naomi Osaka's impressive homecoming moved up a gear as she moved into the semifinals at the Tokyo Open.
Karolina Pliskova's defeat at the US Open means an elated Garbine Muguruza will become world number one on Monday.
Rafael Nadal could meet Roger Federer at the US Open for the first time after outclassing Andrey Rublev in New York.
After a remarkable comeback win over Dominic Thiem, Juan Martin del Potro said he almost retired during the fourth-round clash.
World number one Karolina Pliskova was delighted with her return to form at the US Open, and is ready to face Coco Vandeweghe.
World number one Karolina Pliskova made light work of Jennifer Brady to march into the last eight of the US Open.
While the two finalist were not the marquee names everyone expected, their journey and eventual success is the magic of the US Open.