Mark Selby was far from his best but still did enough to ease past a well below-par Mark Williams 6-1 and set up a semi-final clash with Graeme Dott.

Selby and Williams came back from the jaws of defeat to snatch thrilling wins against Stuart Bingham and Matthew Stevens in their respective last matches, but Friday night's clash was far from a classic.

Despite the comfortable scoreline, the 2008 and 2010 winner did just enough to overcome Williams, who had chances to win the first four frames.

"It was a strange game, I was 3-0 up when I could have been 3-0 down," Selby told

"Mark was nowhere near his best and I found it hard to get focused. He gifted me frames and I picked up the pieces."

"It was a strange game, I was 3-0 up when I could have been 3-0 down" - Mark Selby

Selby, who came back from 5-1 down to edge past Bingham in the second round, took advantage of some sloppy safety play to edge a tight opening frame that lasted 42 minutes.

Williams overturned a 4-1 deficit to beat Stevens and looked set to level proceedings tonight but missed an easy red to hand the initiative to Selby, who duly doubled his lead.

The world number one took advantage of some more lapse safety play from Williams - albeit after Selby had taken control of the table after fluking the yellow - to clear from green to black.

Despite taking a three-frame lead, Selby's highest break to that point was a meagre 28.

However, he continued to show heart for the battle and remained on course to whitewash his opponent as a break of 48 helped him to a 4-0 lead at the interval.

Williams did at least manage to stop the rot in yet another tight frame before Selby put himself one frame away from victory with a break of 73.

He needed two visits to the table to make sure of victory and he will need to step up his performance levels if he is to claim a third Masters crown.