Fermanagh man Brendan Dolan battled his way to a 4-2 win over 19th seed Mervyn King to reach the last 16 of the William Hill World Darts Championship for the first time.
Dolan, who has now knocked two seeds out of the tournament, took the opening two sets at Alexandra Palace before two-time semi-finalist King replied in kind to level the game at 2-2.
Set five went to a last leg decider which went Dolan's way thanks to an impressive 12-dart leg.
The Ulsterman, who landed five ton-plus finishes in the match, won another deciding leg in the sixth set to book his place in round four.
Dolan, who beat 14th seed Joe Cullen on Wednesday, hit seven 180s to his opponent's three but finished with an impressive average above 95.
The world number 36 will play Dutchman Benito van de Pas or Toni Alcinas of Spain for a quarter-final place.
Alcinas and 30th seed Van de Pas will contest their third-round match during the evening session on Thursday.
Dolan said: "I'm feeling confident, having put far more time into my practice routine than I have done in previous years. It feels amazing to come out on top of that one."
On Saturday, fifth seed Daryl Gurney from Londonderry was beaten 4-3 by last year's semi-finalist Jamie Lewis.
James Wade produced a sensational comeback from 3-1 down to defeat Keegan Brown 4-3 in the third round. The Englishman had apologised for controversial post-match comments that he "wanted to really hurt" Japanese opponent Seigo Asada after his previous victory at the Alexandra Palace, blaming his actions on a "hypomanic episode".
Despite enduring a hostile reception from large sections of the crowd and having found himself facing another stern test as Brown moved into a 3-1 lead, there was no repeat of any such outburst.
Wade eventually found his range to take the fifth set 3-0 and went on to progress in the decider against the player who had ended his world title hopes last year. The 35-year-old from Aldershot will face Ryan Joyce for a quarter-final place.
Chris Dobey battled through 4-3 against Vincent Van der Voort, while Adrian Lewis eased through to the last 16 with a 4-0 win over Darius Labanauskas.