Three-time champion Mark Selby suffered a first-round defeat to Mark Williams at snooker's Dafabet Masters on Sunday.
In the tournament's opening match, Williams won a tense deciding frame to clinch a 6-5 victory and book his place in the Alexandra Palace quarter-finals.
Williams, 42, won the Masters in 1998 and 2003 and began against Selby with a break of 135. He moved 2-0 up with an 89 before Selby began to dominate, and at 5-3 ahead the world number one from Leicester looked on course to come through his opening test.
There was more to come from Williams though, and the veteran Welshman hauled himself level.
Selby then inched six points ahead in the decider but missed a difficult last red to give Williams a final chance, and he cleared to the pink to set up a last-eight clash with Barry Hawkins or Kyren Wilson.
Williams said on Eurosport: "I thought it was a good match. Both of us played quite well. I never gave in. I'm over the moon.
"I'm playing a hell of a lot better than I have done for many years. If I can keep playing like that then someone's going to have to play well (to beat me)."
Williams can now be backed at 10/1 with Sky Bet to win the Masters.
Reigning world champion Selby was also eliminated early in the UK Championship last month, losing to Scott Donaldson in the second round.
Mark Allen set up a potential second-round meeting with Ronnie O'Sullivan after a 6-3 victory over Luca Brecel.
The Northern Irishman was in fine form and completed the win with a break of 120 - his second century of the match.
Sunday results & Monday schedule
Sunday January 14
- Mark Selby 5-6 Mark Williams
- Mark Allen 6-2 Luca Brecel
Monday January 15
- Ding Junhui v Ryan Day (1300)
- Judd Trump v Liang Wenbo (1900)
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