Dutchman Raymond van Barneveld beat Michael Smith in a tie-break to reach the PDC World Championship semi-finals at Alexandra Palace.
The five-time world champion fought back from losing the first three sets to win four legs to two in the decider.
He will play fifth seed Adrian Lewis on Saturday, the Englishman having beaten Scotland's Peter Wright 5-2.
In the other semi-final, 2015 champion Gary Anderson will play unseeded Dutchman Jelle Klaasen.
Scotland's Anderson averaged 105 as he demolished three-time semi-finalist James Wade 5-1 in the afternoon session, while Klaasen recovered from a 3-1 deficit to beat Alan Norris 5-4.
Number one seed Van Barneveld, 48, had knocked out world number one Michael van Gerwen in the last 16, but he looked out of sorts as eighth seed Smith dominated the early stages of their quarter-final to take a 3-0 lead.
The Dutchman had been having problems hitting his doubles, but eventually found his range to win 12 out of 14 legs to take a 4-3 lead, including a 110 average in the sixth set.
Former World youth champion Smith was not finished and took the eighth set, then won the opening two legs of the deciding set. He had the chance to close out the match but missed the double top, handing the initiative back to Van Barneveld who took the next four legs to seal victory.
Van Barneveld said: "When I went 3-0 down I thought 'Oh no, this isn't going to happen'. But I told myself to keep believing, and then the fightback began. I cannot describe how happy I am."
Two-time champion Lewis looked at one stage as if he was going to continue his remarkable run of not losing a set in this year's tournament as he took the opening three sets against fourth seed Wright.
Suffolk-based Wright denied him a 15th consecutive set to reduce the arrears to 3-1, then both men swapped sets before Lewis threw a crucial 11-darter that finally broke his opponent's resistance.
Earlier in the day, number two seed Anderson produced some of his best-ever darts to keep alive his chances or retaining the trophy.
|PDC World Championship last four (best of eleven)|
|Saturday, 2 January, 20:00 GMT|
|Raymond van Barneveld v Adrian Lewis||Jelle Klaasen v Gary Anderson|
He found his range straight away and averaged 118 in the second set, in which he missed double 12 for a perfect leg, and 115 in the third.
Seventh seed Wade stopped the rot with a couple of smart check-outs to take the fourth, but Anderson finished on the bullseye to move 4-1 ahead before winning the sixth set with ease.
Klaasen, a former BDO world champion, beat the great Phil Taylor in a thrilling third-round encounter but made a sluggish start against unseeded Norris to trail 3-1.
The Dutchman suddenly came to life, significantly increasing his average and levelling the score at 3-3, only for Norris to take the seventh set missing double 12 for a nine-dart finish.
However, 19th seed Klaasen reeled off two 11-dart legs to make it 4-4 before winning all three legs in the deciding set to sweep into the last four.
"I couldn't hit doubles at the beginning, but I kept fighting and got a few good doubles to eventually break him," said Klaasen, 31.
"I can win the tournament if I play like I have done, but I will have to make it easier for myself by hitting more doubles."