Michael van Gerwen was 1/50 to beat Jeffrey De Zwaan on the opening night of the World Matchplay - but suffered a huge upset at Blackpool's Winter Gardens.
The world number one was odds-on tournament favourite to win his third World Matchplay having already won 15 events this year, including the prestigious Premier League and the Masters.
But one of the titles he didn't win was at the UK Open, where he fell in the third round to De Zwaan in a best-of-19 legs showdown.
Despite that setback in March, MVG was highly expected to get his revenge over the same format and priced up accordingly at 1/50, with the talented young Dutchman rated an 14/1 shot to cause another shock.
But the 22-year-old, who although ranked 68 in the world had won a maiden PDC title earlier in the season, pulled off one of the biggest shocks ever seen in the famous tournament's 25-year history.
As a result, every player has seen their odds slashed for glory, with Gary Anderson now Sky Bet's favourite at 4/1 while Rob Cross is 9/2, Peter Wright 13/2, Michael Smith 10/1 (click here for all the Sky Bet odds).
MVG was not at his best during the first half of the contest and De Zwaan took full advantage, firing in a game-changing 121 checkout to level the tie at 6-6.
De Zwaan then reeled off the final four legs to raise the roof at the Winter Gardens, and set up a second round clash with Adrian Lewis, who beat James Wilson 10-8 earlier in the night.
De Zwaan, who was making his World Matchplay debut, told www.pdc.tv: "I am absolutely over the moon with this win. I always believe in myself, I said to myself 'why can't I beat Michael?' I know I am good enough to do it.
"To win this game on this stage is an absolute dream for me, I have to keep pinching myself!
"Everything has come together for me recently, I'm practicing hard every day and now it is paying off. I'm looking forward to playing Adrian on Tuesday and I want to cause another upset."
In the opening match of the night, former finalist Lewis started well, taking the opening two legs before the Yorkshireman fought back to lead 7-3 thanks to some clinical double hitting.
The two-time world champion dug deep to get himself back in the contest and went within a leg of victory at 9-8 then hit a magnificent 116 finish, the highest of the match, to seal his place in the second round.
"I felt a bit nervous tonight because I've not played on TV for seven months," said Lewis. "It's a relief to get through and hopefully I can push on now.
"When I was 7-3 down I knew I had to find something and I did that. James was fantastic in the first ten legs, I didn't quite have my rhythm at times but I sped up towards the end and got the job done.
"I've been feeling the pressure in first round games all year so it's a relief to get through and hopefully I can push on now."
Premier League runner-up Michael Smith was 33/1 to win his first TV major here in Blackpool due to being in the same quarter of the draw as MVG but he took full advantage of the Dutchman's exit by seeing off Jonny Clayton 10-6 in the last match of the night.
Bully Boy, tipped up by our darts expert Chris Hammer, was made to work hard for the victory by the Welshman in a tight clash.
Fresh from claiming the Shanghai Darts Masters title, Smith was averaging 10 points more than Clayton but leading only 7-6 before rattling off the final three legs to set up an all-St Helens clash with Chisnall in round two.
Four-time quarter-finalist Chizzy ran out a comfortable 10-4 winner against Keegan Brown, growing in confidence as the tie went on after a tricky start.
Brown began brightly, leading 3-2 going into the first break before Chisnall hit back-to-back stunning checkouts of 148 and 147 to take the lead for the first time in the contest.
Although Brown levelled at 4-4, Chisnall continued his charge as the former Grand Slam of Darts finalist rattled off the next six legs without reply to seal his place in the last 16 for a sixth year in succession.
Saturday results & Sunday schedule
Saturday July 21
First Round
- Adrian Lewis 10-8 James Wilson
- Dave Chisnall 10-4 Keegan Brown
- Jeffrey de Zwaan 10-6 Michael van Gerwen
- Michael Smith 10-6 Jonny Clayton
Sunday July 22
Afternoon Session (1300 BST)
First Round (best of 19 legs)
TV Channel: Sky Sports
- Darren Webster v Steve Lennon
- Ian White v Max Hopp
- Gerwyn Price v Joe Cullen
- Daryl Gurney v Steve West
Evening Session (1900 BST)
First Round (best of 19 legs)
TV Channel: Sky Sports
- Mensur Suljovic v Steve Beaton
- Gary Anderson v Stephen Bunting
- Rob Cross v Mervyn King
- Raymond van Barneveld v Kyle Anderson
CLICK HERE FOR FULL WORLD MATCHPLAY DRAW AND SCHEDULE