World number 22 Ricky Walden shocked double world champion Mark Williams 6-3 to reach the quarter-finals of the UK Championship in York.
Walden raced into a 3-0 lead before two-time winner Williams hit back with three straight frames to draw level.
But Walden rallied to win the next three frames, coming from behind in the ninth to seal the victory.
He will meet Shaun Murphy after the world number five held off a dramatic comeback from Martin Gould to win 6-4.
Former world champion Murphy had taken a 5-0 lead after a solid start which included a 102 break in the fourth frame.
World number 16 Gould showed great spirit to win the next four frames in reply, compiling an emphatic 101 break in frame nine.
But Murphy, who won the event in 2005, held his nerve to win a cagey 10th frame despite further heroics from Gould as he attempted to force a decider.
Murphy faces a tough test against Walden in the next round, despite his Cheshire born opponent having won only one ranking event to date.
Walden went into the match with Williams as the underdog, but he took the first frame on the pink before breaks of 56 and 81 fired him into a 3-0 lead.
But Williams battled to a fine 73 break in the following frame and backed it up with breaks of 59 and 54 in frames five and six.
And the world number two looked in control of the seventh frame, but he missed a simple red early on and Walden capitalised with a break of 58.
He then compiled a composed 54 to go 5-3 up before coming back from a 45-point deficit in the ninth to seal a memorable victory.
"I knew I was playing well," Walden told BBC Sport afterwards. "He [Williams] scrapped a few frames out and I knew how good he was.
"I trusted my game and got my chance - I've not had a good run in the TV tournaments, so it's good to come on against a brilliant player like Mark."