Qualifier Alan McManus beat four-time champion John Higgins 13-11 to reach the World Championship semi-finals for the first time since 1993.
McManus, 45, trailed 5-3, 7-5, 9-7 and 10-8, but played with calmness and fluency in the closing stages.
The world number 29 scored four half-centuries and a 128 to win five of the last six frames and will face fellow qualifier Ding Junhui in the last four.
Marco Fu held off a brilliant Barry Hawkins comeback to win 13-11.
Hong Kong's Fu will face world number one Mark Selby, with both semi-finals starting on Thursday.
'Don't call me a veteran'
McManus said his first ranking semi-final appearance since 2006 was not as big a shock to him as it seemed to be to everyone else.
"I can and I can't believe this is happening," he said.
"You guys keep calling me a veteran and I'm thinking 'give me a break'. At 45, I guess I'm getting on a little bit.
"I've never thought these sort of days were completely gone because I can play and I'm still pretty dedicated to the sport.
"I love the game, I love playing and I love playing in big arenas."
Higgins praised his fellow Scot, saying: "The Crucible brings intense pressure and I cracked and Alan didn't. All credit to him. He's still a fine player."
Fu fends off Hawkins fightback
A hopelessly out-of-form Hawkins trailed 7-1 overnight and slipped 9-1 behind in Wednesday's morning session.
But world number 11 Hawkins suddenly discovered the touch that had seen him beat Ronnie' O'Sullivan in the second round to win eight out of nine frames and trail 10-9.
Fu won the next two to close to within one frame of victory and closed out the win with a nerveless 74, despite finally seeing off another brave Hawkins fightback.
"That has to be the best clearance of my life," said a relieved Fu. "I was under a lot of pressure at the end and I couldn't really pot the last ball.
"Some of the shots I played were were horrendous - and I was choosing all the wrong shots. Under pressure, you can think a bit silly.
"I am sure I will disgusted when I look back at some of the shots. I almost threw it away, but luckily I made a good break at the end."