Judd Trump suffered a shock 6-1 defeat to Graeme Dott in the quarter-final of the Masters at Alexandra Palace.
In a match of few high breaks, Dott won the first two frames before the world number two got on the scoreboard.
The Scot then took the next two for a 4-1 lead, and although Trump had a chance in the sixth, Dott pinched it to move within one of victory, before clinching the win with a century.
In the semi-final, he will face Mark Selby who beat Mark Williams 6-1.
The world number one from Leicester triumphed in each of the first four frames, all long, drawn-out affairs, as Welshman Williams missed several good chances.
The two-time world champion finally got off the mark in the fifth, but Selby knocked in 73 to move a frame away from victory, and clinched it in the next.
Earlier, Dott had a much easier task than he had anticipated, telling BBC Sport: "I have not really had any form for the last four to five months. I have been struggling and I am not cueing very well, but I am slowly getting there.
"Luckily for me, Judd did not show up today. You expect him to play well and sometimes when someone doesn't play well, it affects your game. I seemed to struggle too.
"It is unusual for Judd to play as bad as that, but I was happy for this match to be a tactical one."
Having seen the defence of his UK Championship crown end in the first round in December, Bristol's Trump has now failed to produce in the last two majors.
The pre-tournament favourite had to fight back from 5-3 down to beat Barry Hawkins in the previous round, but so poor was his play on Friday there never looked any prospect of a repeat.
Both players missed easy pots throughout, but 2006 world champion Dott ground out frames to establish a comfortable advantage at 4-1.
A break of 54 in the sixth took him to the brink of victory, and he sealed it with a run of 111 in the next to reach the last four of the Masters for the first time.