Top seeds Kyle Edmund and Denis Shapovalov were both upset at the Eastbourne International on Thursday.
Second seed Edmund, who knocked out fellow Brit Andy Murray on Wednesday, lost out to Mikhail Kukushkin 5-7, 6-3, 6-1 on the grass courts on the English coast.
The Kazakh took advantage of Edmunds rising unforced error count late in the match to mount a superb comeback and reach the final four.
Mikhail Kukushkin beats Kyle Edmund, while Denis Shapovalov is also beaten in Eastbourne.
— ATP World Tour (@ATPWorldTour) 28 June 2018
Kukushkin is set to face Mischa Zverev in the semi-finals after the German eased past third seed Shapovalov 6-3, 6-3.
Elsewhere, fourth seed Marco Cecchinato came back from a set down to defeat Australian John Millman 5-7, 6-3, 6-2 to reach the final four.
Waiting for the Italian in the semi-final is Lukas Lacko, who defeated Cameron Norrie 6-3, 6-4 in the opening match of the day.