Mark Selby and Shaun Murphy will meet in the Masters semi-finals after a dramatic day of action at Alexandra Palace.
Murphy saw off Marco Fu 6-4 before Selby battled from 5-3 down to beat John Higgins in a final-frame decider in the evening session.
The pair met in the 2012 quarter-final, won 6-2 by Murphy, though Selby won their UK Championship final that year and their 2007 World Championship semi-final.
The Leicester player had to work hard for his win here, but he led 3-1 at the mid-session interval after responding to Higgins' opening 58 with frame-winning breaks of 42, 70 and 98.
Higgins won a lengthy first frame back with a 43 break after Selby missed a red to the middle, and added a 69 break in the next to level at 3-3.
Selby led in the next after a 56 break but Higgins came back and won a high-quality safety battle on the black to take the frame and a 4-3 lead.
He extended that in the next, Selby desperately unlucky to fail with an escape from a snooker and concede a free ball.
Breaks of 48 and 61 saw Selby win frame nine and he scraped home in the next after Higgins potted a superb yellow but got a horrible kick on the green.
Higgins opened up a lead of 57 in the decider but missed a red, possibly attempting to turn it over with side spin after a poor positional shot. Selby responded by catching the pink to ruin his own position.
Selby laid a magnificent snooker behind the green and though Higgins escaped at the fourth attempt he opened up the reds, pink and black.
Selby was unlucky with a difficult positional shot off the brown and missed another cannon off the pink but after a tense frame, he produced a brilliant clearance including a spectacular double on the blue.
"I'm relieved more than anything," said Selby to www.worldsnooker.com. "I played well before the interval, then after that I struggled.
"In the last frame I thought about playing safe on the blue. But I decided to just go for it full-blooded. I knew I was going towards the pink so if I missed there was a chance I would get away with it.
"John has been struggling recently but in patches it looked as if he was getting his game back. Near the end he missed a few, maybe because of nerves or doubts coming into his head.
"I've watched a bit of Shaun this week and he seems to be playing well and I'm happy for him because I don't want to see my friend struggle. But that will go out of the window on Saturday."
It was the fifth of the 10 matches so far this week to go to a deciding frame. Murphy's win was not one of them, but did require an inspired comeback from the "Magician".
The Sale-based player trailed 3-0 and 4-1 before finding his most fluent break-building form to reel off five frames in succession and win 6-4.
Fu knocked out Judd Trump in round one and began this game with a 76 break to take frame one.
He won the next from 48 behind and added the next and, after Murphy finally got on the board in frame four, Fu restored his three-frame cushion with a 71 in the frame after the interval.
The match turned from then on, though, as breaks of 86 and 81 got Murphy within one frame and a 117 levelled the match.
Frame nine came down to a crucial safety battle on the final red and then the yellow, on which Fu laid a devilish snooker which Murphy twice missed by the narrowest margin.
Fu turned down two potting opportunities, though, and Murphy cleared the colours to lead for the first time.
And he wrapped up victory in the next, taking control with a 64 and finishing things off when Fu left a pot on the green.
Murphy also won the last four frames in his 6-4 first-round win over Ding Junhui and told worldsnooker.com: "One of these days I will start a match as I finish it.
"I keep making things so difficult for myself but I've always had a lot of heart and never given up."