Michael van Gerwen crashed out of the Betfred World Matchplay on Tuesday night, going down 11-4 to Simon Whitlock at the second round stage in Milton Keynes.
Two-time World Matchplay champion Van Gerwen failed to make it past round two for a third successive year, as Whitlock claimed his first win over the world number one since 2016 at the Marshall Arena.
Van Gerwen had won the previous 15 meetings between the pair, but Whitlock took full advantage of the Dutchman's below-par performance to cause the biggest upset of the tournament so far.
"I'm over the moon with that, but I always believe I can beat the best," said Whitlock.
"Michael is the best player on the planet but he had an off-day today and I took advantage of it.
"I just put Michael out of the picture and pretended I was playing local darts.
"I believed in myself and that's the only way to do it. If you play the player you will put yourself in trouble.
"Experience counts for that, and along with a love for the game, that's what keeps us older players going."
Van Gerwen, who follows world number three Gerwyn Price and reigning World Matchplay champion Rob Cross in early exits from the tournament, got off to the worst possible start to trail 5-0.
A rampant Whitlock never allowed his opponent within three legs, as the Australian number one punished Van Gerwen's 20 missed doubles from 24 attempts at the outer ring.
With the three-time World Champion unable to mount a fight back, Whitlock pinned double nine to seal a surprisingly comfortable victory.
Whitlock will now face Gary Anderson in the last 16, after the Scot ran out an 11-8 victory over James Wade in the battle of the former World Matchplay champions.
2018 winner Anderson, who is now the only player left in the field to have lifted the title, threw nine 180s and twice threatened a nine-dart finish by opening the ninth and tenth legs with six perfect darts.
From 3-2 down, Anderson won seven of the next eight legs to move into a commanding 9-4 lead, taking advantage of some uncharacteristic missed double attempts from Wade.
A hat-trick of legs saw Wade fight back to trail 9-7, but Anderson twice found his favourite double top to end hopes of a fightback.
"Tonight was a continuation of how my game has been going recently, some good and some bad," admitted Anderson.
"One minute my throw is fine, the next minute it's all over the place and I'm not quite sure why.
"I found it fine playing the online darts during lockdown, but I'm still finding this very weird playing in front of no fans.
"But, even though I'm not too happy with how I'm playing, I've got that winning feeling so hopefully I can keep it going."
2019 runner-up Michael Smith became the first player to reach the quarter-finals, coming through a dramatic tie-break with Mensur Suljovic to win 14-12.
Smith, who piled in ten 180s, recovered from deficits of 8-5 and 9-6 to take Suljovic to a second tie-break in as many matches.
The opening four legs of the tie-break were shared, with neither player crafting out a match dart, before Smith struck a vital break of throw to go 13-12 up.
After Suljovic spurned three double attempts to break straight back, Smith landed a timely 110 checkout to book a last eight meeting with Krzysztof Ratajski.
"I wasn't ready to go home tonight, I had to fight really hard for my place in the tournament," said Smith.
"I've showed over the last year or so that I have got the fight to stick in games and come out on top.
"People associate me getting annoyed with myself as a sign that I'm 'giving up' but it's not at all, it's me trying to get myself going.
"I often boss games with my scoring but tonight I wasn't scoring well so I had to make up for it with good finishing, which isn't what I'm known for, but tonight I made the most of my chances."
Polish number one Ratajski battled his way to a 12-10 victory over Germany's Gabriel Clemens.
Clemens, who defeated Cross in round one, hit nine 180s but trailed from the first leg of the match until the 18th, when a crucial break of throw saw him tie up the contest at 9-9.
The German number two then hit the front with an 85 finish to hit the front for the first time, only for Ratajski to win a trio of legs to book his place in the quarter-finals on his second World Matchplay appearance.
The night also saw the first round draw to a close, as World Matchplay debutant Dimitri Van den Bergh enjoyed a surprise 10-6 win against Nathan Aspinall.
A hat-trick of 13-dart legs from Van den Bergh helped the Belgian take a firm grip of the game to lead 6-2, before finishes of 103 and a stunning 156 kept the lead out of Aspinall's reach.
Unable to mount a comeback, Aspinall was condemned to back-to-back first round defeats in his first two World Matchplay outings, as Van den Bergh avenged his 2019/20 World Championship loss.
"Winning against a player like Nathan is a great job, I'm very proud of myself," said Van den Bergh, who will meet Joe Cullen in round two.
"Seeing Nathan achieve what he has over the last couple of years makes you focus on yourself and gives you belief that you can get there as well.
"I miss the fans and I miss their support, but even still I feel at home on the stage. I just feel so relaxed up there.
"If I perform for the rest of the tournament how I know I can it doesn't matter who I play."
The second round concludes on Wednesday's Night Five, as 2017 runner-up Peter Wright takes on Glen Durrant in the pick of the ties.
The action will be broadcast live on Sky Sports in the UK, through the PDC's worldwide broadcast partners including DAZN and RTL7, and on PDCTV for Rest of the World Subscribers.
2020 Betfred World Matchplay
Tuesday July 21
1x First Round, 4x Second Round Matches
Dimitri Van den Bergh 10-5 Nathan Aspinall (R1)
Michael Smith 14-12 Mensur Suljovic
Gary Anderson 11-8 James Wade
Simon Whitlock 11-4 Michael van Gerwen
Krzysztof Ratajski 12-10 Gabriel Clemens
Wednesday July 22 (1900)
4x Second Round Matches
Daryl Gurney v Vincent van der Voort
Dimitri Van den Bergh v Joe Cullen
Peter Wright v Glen Durrant
Danny Noppert v Adrian Lewis
First Round - Best of 19 legs
Second Round - Best of 21 legs
Each game must be won by two clear legs, with up to a maximum of five additional legs being played before the sixth additional leg is sudden-death. For example, should a First Round game (best of 19 legs) reach 12-12, then the 25th leg would be the final and deciding