Michael van Gerwen suffered a sensational collapse as he squandered a 5-1 lead against Martin Schindler in the German Darts Masters while Gary Anderson also crashed out.
The world champion has been struggling to find his best form of late, despite winning eight tournaments this season including the Premier League, but looked on course to bounce back from last week's quarter-final exit at the US Darts Masters when he stormed into a 5-1 lead against the world number 53 from Germany.
However he went completely off the boil as the 22-year-old home favourite reeled off five legs on the spin to send the 8,000 fans at the Lanxess Arena in Cologne absolutely wild.
It's actually the second time in a row Schindler has got the better of MVG having beaten him in a last leg decider at a Players Championship event last September - but this was on another level to that on a televised stage.
Van Gerwen averaged just 89 against Michael Smith in Las Vegas seven days ago, missing 12 of his 18 darts at doubles and on this occasion he only managed a mark of 91.75, despite being over 100 when leading 3-0, and spurned eight double attempts.
It was the 11th consecutive match in a row - including his singles matches at the recent World Cup of Darts - where he failed to average 100+ which is obviously incredibly rare for his high standards.
The world number one desperately needs to recover in time for the World Matchplay, which gets under way in Blackpool next weekend, as he bids to win the prestigious title for a third time.
Schindler to his huge credit never gave in when starring defeat in the face and punished MVG for three missed match darts spanning the eighth and ninths legs before taking the last two in 13 and 14 darts respectively.
"It's an amazing feeling, I just can't even put it into words," said two-time World Cup of Darts quarter-finalist Schindler. "I was shaking so much, I don't know how I won that game but I did it and right now I'm just so, so happy.
"This may be the biggest win of my career, I'm not even sure at the moment but when it sinks in I think it will be my biggest win."
Nico Kurz also caused a huge shock earlier on the night as he hit a 170 checkout en route to defeating Anderson.
The 22-year-old German is relatively unknown having only played once before in a televised PDC event - at this same tournament last year when he was beaten in the opening round - and is ranked down at 181 in the world.
But Kurz, who did at least gain some stage experience at a European Tour event earlier this season, showed no sign of stage fright in front of huge crowd as he defeated the legendary Flying Scotsman.
Having settled nerves with a 116 checkout in the opening leg, he thrilled the home fans with the Big Fish from 170 to edge ahead in the fifth leg while he punished the two-time world champion for a missed dart at double top by finishing 74 for a 4-3 lead.
Anderson, who had produced a 138 checkout to level in the sixth, then fell 5-3 down before a 79 finish kept him in the contest but that would be the last leg he'd win as Kurz held his nerve for a famous World Series victory.
Kurz didn't hit a single 180 but he did averaged 95.03 and converted six of his 10 attempts at doubles. Anderson hit three maximums, averaged 92.8 and missed 10 doubles.
"This is the biggest win of my career, I think I've never been so happy in my life," said Kurz, who became the first German winner on the World Series. "Gary has always been a role model for me, he is one of the best players of all time. I still can't believe what I achieved today.
"I tried to focus on my game and not to pay attention to Gary or the amazing crowd, and I think it went pretty well!"
The German youngster will now face Anderson's World Cup of Darts winning team-mate Peter Wright after he survived a scare against Robert Marijanovic.
Snakebite was cruising when averaging over 100 at 5-1 up and his sparkling run included a 100 checkout and another from 92 consisting of a pair of double 18s.
But Marijanovic suddenly decided to turn up and three legs later he hauled himself back to 5-4 down with a fine finish from 114.
His comeback would be in vain, however, as Wright hit his third 180 of the match en route to a closing 13-darter, which helped his average up to 96.69.
Gabriel Clemens, tipped up at 80/1 each-way on these pages along with 10/1 shot Wright, made an impressive start as he defeated Raymond van Barneveld 6-4 to reach the quarter-finals.
The German Giant is considered by many observes to be the best player in his country at the moment despite being ranked below Max Hopp and Martin Schindler while few will be surprised by this result.
Whereas Barney has been struggling badly during his final season before retirement, Clemens has reached two Players Championship finals and this could be a prime opportunity to show his quality on the televised stage.
He averaged 98.48 compared to Barney's 90.39, hit two 180s, pinned six of his 10 attempts at doubles and completed victory with a 77 checkout.
The German crowd were delighted to have three players reaching the quarter-final but their number one favourite Max Hopp couldn't join them despite a fantastic display against Rob Cross.
Roared on by the partisan fans, the Maximiser averaged 106.62, hit four 180s, missed just one double from five attempts and managed two 100+ checkouts, including one from 144 in the very first leg.
Any other match this kind of display would have been good enough to win but Voltage's 100% checkout percentage and 101.41 average denied him.
There were no problems for 2018 World Series of Darts Finals champion James Wade as a pretty mediocre average of 90.7 was enough to cruise past Kevin Munch 6-2 in the opening match of the night.
Munch, who hasn't done much of note since famously shocking Adrian Lewis from two sets down at the 2018 World Championship, was never in the match as he averaged just 82 although he did only miss one dart at a double.
Daryl Gurney also won by the same scoreline in his clash with Christian Bunse although the 2018 Players Championship Finals winner was somewhat fortunate that his opponent was so wasteful with his finishing.
Making his televised debut, Bunse blew eight darts at doubles but despite that still managed a creditable average of 92.82 while Gurney, who averaged 97.2 with three 180s, was far more clinical, pinning six of his 10 double attempts.
Mensur Suljovic had an easy time of it as he brushed aside Maik Langendorf 6-2 with an average of 90.86 and a pair of 100+ checkouts.
Saturday's action will see the tournament conclude, live on ITV4, with the quarter-finals, semi-finals and final all in one night.
German Darts Masters: Results and schedule
Friday July 12
First Round (Best of 11 legs)
TV Coverage: ITV4 from 8pm BST
- James Wade 6-2 Kevin Munch
- Gary Anderson 4-6 Nico Kurz
- Daryl Gurney 6-2 Christian Bunse
- Peter Wright 6-4 Robert Marijanovic
- Raymond van Barneveld 4-6 Gabriel Clemens
- Mensur Suljovic 6-2 Maik Langendorf
- Michael van Gerwen 5-6 Martin Schindler
- Rob Cross 6-4 Max Hopp
Saturday July 13
Quarter-Finals (Best of 15 legs)
TV Coverage: ITV4 from 8pm BST
- Peter Wright v Nico Kurz
- Daryl Gurney v James Wade
- Martin Schindler v Mensur Suljovic
- Rob Cross v Gabriel Clemens
Semi-Finals (Best of 15 legs)
- Winner QF 1 v Winner QF 2
- Winner QF 3 v Winner QF 4
Final (Best of 15 legs)
- Winner SF 1 v Winner SF 2
World Series of Darts: 2019 Event Calendar
- US Darts Masters – July 4-5, Mandalay Bay Resort & Casino, Las Vegas (Winner: Nathan Aspinall)
- German Darts Masters – July 12-13, LANXESS Arena, Cologne
- Brisbane Darts Masters – August 9-10, BCEC, Brisbane
- Melbourne Darts Masters – August 16-17, Melbourne Arena
- NZ Darts Masters – August 23-24, Claudelands Arena, Hamilton
- World Series of Darts Finals - November 1-3, AFAS Live, Amsterdam