Third seed Nikolay Davydenko wore down Czech Tomas Berdych to seal a 5-7, 6-4, 6-1, 7-6 victory and reach the quarter-finals.
Russian Davydenko was outplayed by the 13th seed in the first set but his unerringly consistent game gradually nullified the 21-year-old Berdych and he clinched victory on his fourth match point in exactly three hours.
Berdych saved three match points at 5-6 in the fourth set to force the tiebreak but he made two unforced errors to give Davydenko match point and another mistake sent the Russian through to the last eight.
Davydenko will play Haas for a place in the semi-finals.
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Celebrities at the Australian Open
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