THREE-TIME champion Mark Selby suffered a first-round defeat to Gwent's Mark Williams at the 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.

Cwm potter Williams, aged 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)."

Reigning world champion Selby was also eliminated early in the UK Championship last month, losing to Scott Donaldson in the second round.