Stephen Maguire converted his fourth consecutive world-ranking quarter-final into a place in the semi-finals of the Welsh Open at Newport with a 5-3 win over Mark Williams, winner of the German Masters earlier this month.

"I've underachieved in the last couple of years," Scotland's world No6 said. Williams agreed: "A lot of the time he beats himself up. If he sorts that out he'll win tournaments."

Maguire cleared with 65 for the black-ball win that enabled him to level at 2-2 and with 105 to equalise at 3-3. He clinched the seventh with 68 after early errors on both sides and, with the aid of a decisive stroke of luck, added the untidy eighth for victory.

Mark Selby, twice Masters champion but with the 2008 Welsh Open still standing as his sole ranking title, led Graeme Dott 4-1 and beat him 5-3 to bring himself against Maguire today.

Dott was unimpressed that his run to the last eight deprives Ronnie O'Sullivan of ninth place in the rankings: "The way Ronnie's playing that's nothing to brag about."