Ryan Day knocked four-time world champion John Higgins out of the World Grand Prix in a dramatic finish.
Higgins recorded breaks of 104 and 103 and levelled the match three times.
But Welshman Day clinched his place in the quarter-finals by sinking a final-frame black for a 4-3 win in Llandudno.
"It was a bit of an awkward clearance, which I managed to hold myself together and make it through. It was an enjoyable match to be involved in and one I'm pleased to win," said Day.
With Mark Williams, Michael White and Jamie Jones all out, Day is the only Welshman left in the tournament.
He'll take on world champion and world number two Stuart Bingham on Friday.
Bingham beat defending champion Judd Trump 4-2 and both players complained of ill health afterwards.
Trump said he had tonsillitis while Bingham revealed he would be going back to bed because of flu symptoms.
Ding Junhui beat Peter Ebdon 4-0, while Thailand's Thepchaiya Un-Nooh won 4-2 against Mark Allen.
Ding and Un-Nooh will face each other in the first quarter-final at 13:00 GMT on Friday.