Mercedes again look set to dominate Formula One racing this year, judging by Australian Grand Prix opening practice times on Friday.

But mystery surrounds the Sauber team after both drivers failed to emerge for the 90-minute session at Albert Park amid a legal stoush.

German Nico Rosberg topped the time sheets by clocking one minute, 29.55 seconds ahead of Mercedes teammate and defending world champion Lewis Hamilton (1:29.58).

Williams’ Valtteri Bottas (1:30.74) was third fastest, more than a second behind Mercedes.

Mercedes picked up where they left off from last season when they emerged as an F1 force to be reckoned with.

Hamilton tussled with Rosberg all season before winning six of the last seven races to claim his second world title in 2014.

Red Bull’s Australian driver Daniel Ricciardo was the only non-Mercedes competitor to claim race wins last year, notching three.

Local hero Ricciardo made a cautious start on Friday, clocking the 10th fastest time (1:31.57).

Four-time world champion Sebastian Vettel, 27, made his official debut for Ferrari, finishing fifth fastest (1:31.02).

He left Red Bull at the end of last year after being backed by the team since he was 12.

However, there were more questions than answers for the Sauber team after both drivers Marcus Ericsson and Felipe Nasr failed to emerge for the session.

It is still unclear whether they will comply with a Victorian Supreme Court order to allow driver Giedo van der Garde to race.

The Dutch driver on Friday reportedly started to be fitted to drive in Ericsson’s place for the season opening F1 race as the lengthy legal battle continued in the Victorian Supreme Court.

The second practice session starts at 1430 AEDT.