Top seed Roger Federer survived a testing examination from Russian fifth seed Nikolay Davydenko before winning 6-4 3-6 7-6 7-6 to reach the Australian Open semi-finals.
The world number one was pushed all the way by Davydenko but his sublime skills and unrivalled ability to raise his game when it matters enabled the Swiss master to book his place in the last four against German Nicolas Kiefer.
Federer was pushed to five sets in his fourth round match with Tommy Haas and it briefly looked as though he might have to go the full distance again after the Russian pinched the second set and served for the third.
But Federer broke back when he needed to and then saved six set points before taking the third set in a tiebreak and then won the fourth in another tiebreak to remain on course for his second Australian Open crown.
Earlier in the day, Kiefer overcame Frenchman Sebastien Grosjean 6-3 0-6 6-4 6-7 8-6 in an ill-tempered quarter-final to reach his first grand slam semi-final in 35 attempts.
Both players were involved in an angry exchange after trading shots at the net in the 12th game of a tense fifth set after Kiefer threw his racket as Grosjean was playing.
The Frenchman missed an easy volley and the point was awarded to Kiefer. Grosjean protested bitterly to chair umpire Carlos Bernardes and match referee Mike Morrissey but the point stood.
Twenty-first seed Kiefer, who complained often about line calls and was earlier handed a code violation for swearing, broke a tiring Grosjean's serve in the 14th game of the fifth set to close it out after four hours and 48 minutes, the longest match of the tournament.
He will play either top seed Roger Federer or fifth seed Nikolay Davydenko in the semi-finals.
