Sixteen-time champion Phil Taylor beat Vincent van der Voort to set up a PDC World Championship semi-final with Raymond van Barneveld.
Taylor, who last won the title in 2013, edged a tense see-saw match 5-3 despite losing three successive sets.
The 54-year-old said: "It felt more like survival than a victory but I'm through and that is all that matters."
Dutchman Van Barneveld trailed BDO world champion Stephen Bunting 3-2 but fought back to win 5-4.
The five-time champion broke Bunting's resistance with a 107 checkout to take a tense seventh set and followed it up with a 113 checkout against the darts at the start of the last set.
In the earlier contest, Taylor was far from his best, averaging 100.08 with just a 40% success rate with doubles, but was fortunate that Dutchman Van der Voort struggled with a back injury.
The turning point came in the sixth set when Taylor, trailing 3-2, won the decisive leg despite taking 8 darts to hit a double.