Nathan Aspinall ended Gerwyn Price's reign as BoyleSports Grand Slam of Darts champion in a second round classic in Coventry on Saturday, as Michael van Gerwen, Michael Smith and Damon Heta completed the quarter-final line-up.
Price had been aiming to lift the Eric Bristow Trophy for a third successive year and showed his class by coming from 7-3 down to lead 8-7.
However, Aspinall regained his composure to win the next two legs, and when Price missed two darts at double four to take the game into a deciding leg, he took out 92 on the bull to claim a memorable win.
"It's a massive win for me," said Aspinall. "We always have fantastic games and it was one of the most enjoyable games I've ever had.
"He brings the best out of me and I knew I had to score well tonight and finish well.
"I missed six darts to go 8-7 up and to not let that affect me, and to come back the way I did to win the last three legs I'm very happy and proud of myself.
"I've been struggling of late, not been playing very well, and I knew I had to bring my A-game tonight. I dug deep and played some good stuff."
After Price had taken out 110 to level in leg four, Aspinall took command with four straight legs and finished 94 for a 7-3 cushion.
The Welshman dug deep in his quest to retain the title, finishing 70, 87, 105 and 75 in his five-leg burst to move ahead for the first time since the opening leg.
However, it was Aspinall who had the final say as he moved through to set up a quarter-final tie with World Matchplay champion Dimitri Van den Bergh on Sunday evening.
"I owe him one because he's won our last two games on TV, in the World Matchplay and in the Group Stage earlier this week," added Aspinall.
"He's a different player now than he was six months ago, and the last two times I've played him I struggled to get any kind of adrenaline going. He's very tough for me to play against.
"I've learned something tonight about my game and I'm going to be pumped up and ready for him tomorrow."
Michael van Gerwen powered into the quarter-finals with a 10-2 defeat of Gary Anderson to continue his bid for a fourth Grand Slam title.
The world number one's return to top form continued as he averaged 102 and defied six 180s from long-standing rival Anderson to clinically set up a quarter-final against Simon Whitlock on Sunday evening.
Anderson responded to an opening 14-darter from Van Gerwen with a brilliant 132 bull checkout in leg two, but paid for five missed darts at doubles as the Dutchman embarked on a run of eight straight legs.
Van Gerwen took out 92, 88 on the bull and 87 at key moments as he moved 9-1 up, and though Anderson finished 81 to keep alive his hopes, any chance of a fightback was ended as a 76 finish moved the three-time winner into the last eight.
"I'm still in the tournament and I feel I played well," said Van Gerwen. "
"There's still room for improvement but I'm happy, and I think I did the right things at the right moments - I hit a couple finishes early doors which gave me confidence.
"Gary played okay in some patches but has a lot of problems with his knee - but if someone's competing in the tournament you have to beat them, simple as that."
Van Gerwen lost to Whitlock in both the World Matchplay and World Grand Prix earlier this year, and added: "Simon beat me before so I've got something to put right, and he is playing some phenomenal darts lately.
"He's starting to get back to good form, but it's up to me to answer that and make sure I do exactly the same back. I know if I play my game, I'm going to beat him."
Michael Smith held his nerve in a deciding-leg shoot-out against Rob Cross to reach the BoyleSports Grand Slam of Darts quarter-finals for a second successive year with a narrow 10-9 victory.
Smith had looked to have blown his opportunity to win a tight contest after seeing three match darts go begging in leg 17, as Cross finished 70 and then landed tops to force a deciding leg.
The world number four, though, followed 11 earlier 180s by kicking off the final leg with a 177, before pinning double 12 for a 13-darter to set up a last eight last with Jose De Sousa on Sunday.
Cross had earlier come back from 2-0 down to lead 3-2 and also took out a match-high 119 finish as he moved 6-5 up, but a three-leg surge from Smith proved key as he edged clear in the second half of the contest.
"I'm happy but also a bit frustrated because I could have wrapped it up earlier, but I'm proud of how I handled that last leg because I could have buckled," said Smith. "I wanted it so much and I'm happy.
"I was a bit patchy in the game but it was a tough game for me tonight, especially against Rob. He's got a great record against me so it's about time I got one back.
"It was a battle but I can put that to one side and it's a new game tomorrow against Jose. I'm glad I'm in the quarter-finals, it's a tournament that I love and I'm looking forward to tomorrow now."
Damon Heta reached his first televised ranking quarter-final with a 10-7 win over Devon Petersen to create a rematch with James Wade on Sunday.
The Australian ace had lost out 5-2 to Wade in the opening game of the Group Stage on Monday, but will now get the chance to avenge that loss in a knockout clash after proving too strong for Petersen.
Heta opened up leads of 4-1 and 8-3 to punish a slow start from Petersen, who hit back to 8-6 at one stage.
However, Heta's brilliant 144 checkout in leg 15 - with Petersen waiting on 40 - proved crucial before he closed out the win two legs later.
"I'm stoked," said Heta. "I knew what I was in for but Devon didn't show up as well as he normally does and I took my chances when I got them.
"I was expecting a really tough, close game because I know how good a player Devon is.
"The 144 was very crucial and I had to take it out, and I think that crushed him a little bit because he was getting the momentum back."
The 2019 Brisbane Darts Masters winner added: "I'm looking forward to playing James. I lost to him in the Group Stages and he's such a steady player. I could learn a lot from James but I've beaten him a couple of times and I'll try and do the same again."
Going into Sunday's quarter-finals, Van Gerwen is now the 5/4 tournament favourite with sponsors BoyleSports to claim the title on Tuesday evening.
Aspinall is 6/1 to claim his third televised ranking title, while Van den Bergh is priced at 13/2 to follow up July's World Matchplay win with Grand Slam glory.
The tournament is being broadcast live on Sky Sports, as well as through the PDC's international broadcast partners including RTL7 and DAZN and for PDCTV Rest of the World Subscribers.
BoyleSports Grand Slam of Darts
Saturday November 21
Michael Smith 10-9 Rob Cross
Damon Heta 10-7 Devon Petersen
Michael van Gerwen 10-2 Gary Anderson
Nathan Aspinall 10-8 Gerwyn Price
Sunday November 22
Afternoon Session (1300 GMT)
Michael Smith v Jose De Sousa
Damon Heta v James Wade
Evening Session (1900 GMT)
Nathan Aspinall v Dimitri Van den Bergh
Michael van Gerwen v Simon Whitlock
BoyleSports Grand Slam of Darts
Outright Winner Odds - Before Quarter-Finals
5/4 Michael van Gerwen
6/1 Nathan Aspinall
13/2 Dimitri Van den Bergh
7/1 Michael Smith
8/1 James Wade
10/1 Damon Heta
11/1 Jose De Sousa
25/1 Simon Whitlock
Odds correct at time of writing and courtesy www.boylesports.com. Subject to fluctuation.