Andy Roddick won the battle of the big-hitting former grand slam champions in four sets to bring an early end to Marat Safin's challenge.
The sixth seed triumphed 7-6 (7/2) 2-6 6-4 7-6 (7/2) over the 26th seed to secure a last-16 encounter against Croatia's Mario Ancic.
Roddick won his lone major at the 2003 US Open but has been playing well for the past six months since convincing Jimmy Connors to be his coach.
Connors just joined Roddick Down Under after the death of his mother, Gloria.
Safin won the US Open in 2000 and the Australian Open two years ago, but more recently has been plagued by injuries.
Prior to this Melbourne meeting, the Russian had won the last match between the two - a straight-sets victory on clay in last year's Davis Cup semi-finals.
Roddick now holds a 4-3 head-to-head record over Safin, and will next face ninth seed Ancic, who crushed 22nd-seeded Slovakian Dominik Hrbaty 6-3 6-2 6-1.
