Selby conquered Stephen Hendry earlier in the tournament

The world number five trailed 3-1 at the interval and 4-2 but runs of 55, 103 and and a pressure break of 54 in the final frame sealed a memorable win.

"I'm gobsmacked to still be in the tournament," said Selby, who will face Ken Doherty in the last four after the Dubliner edged out Shaun Murphy 6-5.

Doherty fought back superbly from 4-1 down to win another last-frame decider.

The former world champion looked dead and buried at the mid-session interval but notched three century breaks - 141, 114 and 123 in the decider - in the last four frames to snatch victory from Murphy's grasp.

"It was up there with my best performances - not just in winning but the way I played with three centuries in four frames at the end," said Doherty.

Murphy added: "There's never any disgrace in losing to someone who's playing as well as Ken was."

Selby had taken the first frame of the afternoon match with a break of 58 but lost a close second and saw Maguire put in a break of 105 on his way to a 3-1 lead at the interval.

Luckily I was able to stamp my authority on the game and didn't give him much of a chance in the last three frames Mark Selby

The first frame after the break went Selby's way, but this season's Northern Ireland Trophy champion and UK Championship finalist Maguire earnt himself a two-frame cushion with an excellent 67 to edge 4-2 ahead.

It could have quite easily gone 5-2 in the Scot's favour, but having failed to add to a composed break of 59, Selby struck to take the frame just when it looked as though it had slipped through his grasp.

A break of 30 did the trick, the 24-year-old Leicester cueman winning the frame on the final black.

Selby should have levelled at 4-4 but missed a simple yellow ball to square matters as Maguire went 5-3 ahead.

"Overall, apart from the last three frames, Stephen was probably the better player," Selby added.

"But luckily I was able to stamp my authority on the game and didn't give him much of a chance in the last three frames.

I just can't believe I've got beat Stephen Maguire

"Funnily I felt more relaxed when I was 5-3 down, so I'm looking forward to the semi-finals. Maybe I'll go 5-3 behind and then see what happens.

"I'm a bit fortunate to still be in the tournament, but if I am destined to win it then I'd be chuffed to bits."

Maguire was suitably shocked after seeing his winning position disappear.

"I just can't believe I've got beat," said the Scot, provisionally number two in the world rankings. "I was thinking I was in the next round, but he stepped up a gear and played great.

"Even when it went 5-4 I thought if I got my chance I'd finish it. I find it hard to take, 5-3 up was the right scoreline, but he missed a bad yellow to make it 4-4.