World champion Mark Selby has been knocked out in the last 16 of the Welsh Open by Belgian youngster Luca Brecel.
Selby was seeking back-to-back titles after he won the German Masters earlier this month but slipped to a 4-3 loss to Brecel, ranked 66th in the world.
Brecel, 19, told World Snooker: "I was confident. That's the thing I worked on hard - how to beat the top players."
Meanwhile, John Higgins secured a place in the quarter-finals with a 4-2 victory over Michael Georgiou.
World number one Selby, 31, led 2-0 and then 3-2 in Cardiff but Brecel, who became the youngest player ever to compete at the Crucible back in 2012, took the crucial sixth frame following a 101 break.
In the final frame Brecel built a 46-0 lead before the Englishman missed a red to the top corner. The Belgian then kept his nerve to close out the match.
He will face either Stuart Bingham or Ricky Walden on Friday.