Former world champion John Walton bowed out of the BDO World Championship after losing 3-1 to Yorkshire rival Martin Atkins at the Lakeside.
Seventh seed Walton, who won the 2001 title, won the first set but struggled to hit his doubles after that as unseeded Atkins closed out victory.
Another seed to be knocked out was Jan Dekker, who fell 3-2 to fellow Netherlands player Christian Kist.
Another Dutchman through is Willy van de Wiel who beat Dave Prins 3-0.
Number two seed Scott Waites also avoided an upset, beating fellow Englishman Andy Boulton 3-1.
Former champion Ted Hankey survived Clive Barden's comeback to win 3-2, while Wesley Harms brushed off the challenge of Martin Phillips with a 3-1 victory.
Paul Jennings rode his luck a little before overcoming Garry Thompson 3-1 in another all-English clash.
However, it was Atkins who took the headlines for his shock defeat of Walton.
"I was confident I'd give John a good game but I didn't think I'd win," Atkins told BBC Sport.
"But John will always give you chances as he misses a few doubles."
Defending women's champion Trina Gulliver cruised through to the semi-finals with a 2-0 victory over Lisa Ashton.
It was an emotional victory for Gulliver, whose mother Muriel died two days before the tournament began.