British number three Cameron Norrie's run at the St Petersburg Open was ended in the quarter-finals by in-form Russian Andrey Rublev.
Norrie, 25, had beaten American eighth seed Taylor Fritz and Serbia's Miomir Kecmanovic, but third seed Rublev proved too strong in a 6-2 6-1 win.
Norrie struggled on serve and Rublev broke for a fifth time to seal victory.
Rublev, 22, has won a career-best 32 matches in 2020, with only Novak Djokovic winning more on the ATP Tour.
World number 10 Rubley, who is aiming to qualify for the end-of-season ATP Tour Finals for the first time, moved closer to that target with a clinical 63-minute win against Norrie.
In the semi-finals, Rublev will face Canada's Denis Shapovalov after he won 6-4 7-5 against Swiss three-time Grand Slam champion Stan Wawrinka.
The match has extra significance with 21-year-old Shapovalov also bidding to reach the season-ending finals at London's O2 Arena next month.