Three-time champion Martin Adams was knocked out of the BDO World Darts quarter-finals as Jan Dekker produced a thrilling 5-2 win.
Dekker led 3-0 but after Adams won the next two sets the Dutchman held his nerve to secure a memorable victory at Frimley Green.
He will now face Alan Norris, who beat fellow second seed James Wilson 5-2 in Friday's other quarter-final.
Top seed Stephen Bunting faces Robbie Green in the other semi-final.
Dekker surged into a 3-0 lead but Adams checked out with a 161 to pull a set back before closing the gap to one set.
But the Dutchman responded after falling two legs down in the sixth set to move 4-2 ahead.
After missing five match darts, Dekker held his nerve to win the seventh set and reach his second semi-final.
Norris and fellow Englishman Wilson were level at 2-2 at the interval but Norris pulled away to reach the last four.
In the women's tournament, England's Lisa Ashton reached the last four with a 2-0 win over Tamara Schuur of the Netherlands.
She will face Russian Anastasia Dobromyslova, who beat England's Fallon Sherrock 2-1.