Lewis Hamilton was fastest in Saturday morning's free practice session, edging Sebastian Vettel by just 0.264s as the duo sharpened their weapons before this afternoon's qualifying shootout.
But Charles Leclerc was just 0.457s adrift as he backed up the suggestion that Ferrari is finally starting to unlock the speed of its SF90.
It was a muted session for Red Bull, with Pierre Gasly clocking in sixth and Max Verstappen only ninth fastest.
'Best of the rest' honors in the session went to the fast moving Haas drivers, with Romain Grosjean and Kevin Magnussen respectively P4 and P5, while Valtteri Bottas was only seventh fastest.
Verstappen was the first driver to head out on track for Saturday morning's final practice session before this afternoon's qualifying.
The Red Bull driver was given a new chassis overnight , apparently as the result of a fuel-tank leak on his original RB15, with a chassis swap a faster process than replacing the tank itself.
Installation laps were the norm as usual in the opening stages of the sessions, although both Williams drivers - who were predictably slowest on Friday - were hard at work at the outset.
Verstappen headed the timesheet early on but was bumped off the top by a run on soft tyres for Toro Rosso's Daniil Kvyat.
Evidently, the widespread use of Pirelli's red-rimmed rubber meant that qualifying simulations were in order as everyone prepped for the afternoon's grid-defining showdown by getting a feel for the soft compound.
Both Hamilton and Vettel were late to join the action, but when they did, lap times tumbled. The Ferrari driver shaved a second off Kvyat's time to put a 1m23.739s on the board, but Hamilton's first flyer edged the German by 0.040s.
Bottas also got going, slotting himself second behind his team mate who then lowered his time to a 1m23.360s.
Meanwhile, Kubica unnecessarily clouted the pit lane entry, damaging the front wing on his Williams, a clumsy mishap which the team will have likely frowned upon given its lack of spare parts in Melbourne.
Fifteen minutes from the end of the session, a soft-shod Vettel jumped the leading Mercedes duo with a flawless 1m22.556s that perhaps provided a glimpse into Ferrari's true colors and the speed it demonstrated in pre-season testing. Or were track conditions simply improving?
Regardless, it was game on at the front, with Hamilton - also on the soft rubber - clocking in 0.264s faster than his arch-rival!
Leclerc was third behind the dueling duo, while the Class B field was led by the fast-moving Haas drivers, with Grosjean and Magnussen respectively P4 and P5!
Red Bull's chargers struggled to hold their own however, with Gasly concluding the session P6 while Verstappen lingered down in ninth, behind Kvyat and in front of Renault's Daniel Ricciardo who rounded off the top-10.
The reigning world champion has the upper hand heading into qualifying but Vettel is definitely in the hunt. The posturing is over and it should be a thrilling shootout around Albert Park in two hours' time, don't miss it!