Welshman Clayton ended reigning champion Michael van Gerwen’s 21-game Grand Slam winning run in the group stage in dramatic fashion on Sunday, and continued his run last night thanks to a magnificent 103.65 average.
Clayton limited the Polish star to just five darts at a double in the 13 legs, landed five180s and took out almost 60 percent of his own shots at a double.
The 44-year-old now progresses to a quarter-final tie at the Aldersley Leisure Village on Saturday as he aims to capture his maiden TV title.
“This is massive for me, I’m loving every minute of my time spent in this tournament,” said Clayton.
“Anything beyond the group stage is a bonus for me. I just wanted to make sure I kept straight and thankfully I managed to play really well again.”
German newcomer Unterbuchner caused the biggest upset of this year’s tournament by ending Wade’s bid to claim a third successive televised title.
BDO qualifier Unterbuchner claimed a 10-6 victory to book his place in the quarter-finals in his Grand Slam debut.
Wade was hoping to extend his winning run on TV to 14 matches but Unterbuchner punished his missed doubles to upset the odds and claim a famous win.
“It’s unbelievable to beat James Wade, such a fantastic player on this amazing stage,” said Unterbuchner.
“I booked my flights home because I didn’t think I would win but I don’t mind staying longer, hopefully until Monday!”
Unterbuchner now plays Gary Anderson on Saturday night, after the two-time world champion raced past Dutchman Wesley Harms with a dominant 10-2 triumph, averaging over 101 in the process.
Anderson raced into a 3-0 lead, with Harms cutting the gap to one with back-to-back legs only for Anderson to pull away as he followed an 11-darter with a 136 checkout to regain breathing space.
Six straight legs moved Anderson to the brink of victory at 9-2, before he completed the win to maintain his push for a fifth televised title of 2018.
The quarter-finals begin tonight as nine-dart hero Dimitri Van den Bergh – who achieved perfection in his second round win over Stephen Bunting – plays Austrian star Mensur Suljovic.
Australia’s Simon Whitlock then faces Welshman Gerwyn Price.