Belgian Dimitri van den Bergh remains in contention for back-to-back World Matchplay titles after knocking out champion Gerwyn Price 16-9 in the quarter-finals in Blackpool.
Van den Bergh, 27, never lost the lead in a dramatic battle at a sweltering Winter Gardens.
The World Matchplay is the only ranking semi-final Price, 36, has not reached.
It was even in the opening legs of the match, as both players held their throw until the fifth leg.
That went the way of the Belgian who threw a 14-darter to take a 3-2 lead.
Price's failure to hit the doubles meant he was unable to break Van den Bergh in the sixth leg with the latter taking five straight legs.
Walking out to boos again from the crowd, world number one Price did not look comfortable until he stopped the Belgian's run in the ninth leg to hold his throw.
Price's trademark roar reverberated around the Empress Ballroom and seemed to ignite the Welshman's fire and he broke Van den Bergh's throw in the next leg to close the lead to 6-4 at the second interval.
Van den Bergh fought back to break the Welshman again in the 11th leg and both players held their throws until Price broke back in the fourteenth leg make reduce the Belgian's lead to 8-7.
Both players held their throws after the third interval with very little to separate them, with their averages about 100.
In the 19th leg, Price missed his usually reliable double tops and double 10 to make it 10-9 and Van den Bergh capitalised on the Welshman's uncharacteristic errors to extend his lead to 12-8.
The defending champion took control of the remaining legs of the match as the pressure piled on the world champion, who kept missing doubles to finish. Van den Bergh threw a 102 average to eventually win 16-9.
"It was a mad game. I'm ecstatic, I'm sky high, there are no exact words to describe how I'm feeling," said Van den Bergh.
"I was nervous but I stayed focused and at certain times I felt lucky with Gerwyn as he missed a few darts at the double.
"Gerwyn's the world champion and world number one and it's incredible to be playing against him - I like him, he's a great man and I have a lot of respect for him," Van den Bergh added.
In the evening's other quarter-final, Poland's Krzysztof Ratajski cruised into the semi-finals of the World Matchplay for the first time after beating debutant Callan Rydz 16-8.
It is the first major semi-final for Ratajski, 44, who broke Rydz, 23, in the second leg to take an early lead which he never relinquished.
Consistent high scoring from Ratajski, averaging 97 compared to 88 for Rydz, as well as solid finishing meant the youngster was only able to break his opponent twice late into the match.
"I'm over the moon, it's something really big for me. I'm so happy to win this match," said 13th seed Ratajski.
"I hope I play in the semi-final with less mistakes as I did many mistakes on the doubles and there was a moment I was happy with my game."
Ratajski will meet Van den Bergh in the semi-final on Saturday night, a prospect he says he won't worry too much about.
"Every match is a different story, it doesn't matter who I play. It will be a very big match for me and I expect myself to play at a better level than I did tonight," Ratajski added.
Van den Bergh says the best is yet to come from him, "I believe that I'm still developing and I'm not at my best yet.
"In my eyes Ratajski is under-valued, I'm going to play the Polish champion in the semi-finals and that's the same as playing the world champion in my eyes.
"It's going to be a big battle on Saturday but I know how good Ratajski is and he showed it again today. He's fantastic and I've got to be focused and believe in myself.
"It would be unbelievable to be one of those players who defends this title but I've got to keep my feet on the ground," added Van den Bergh.
Friday night sees the other side of the draw in action with 2017 runner-up Peter Wright facing 2019 runner-up Michael Smith in the first match of the evening.
This will be followed by two-time Matchplay winner Michael van Gerwen against world number 11 Nathan Aspinall, who had not won a match in Blackpool until this year.