New coach Guus Hiddink handed the skipper's armband to the Middlesbrough forward in the absence of regular captain Craig Moore, who was unavailable because of a hamstring injury.
'It's a big surprise to me. It's a great honour and I can't wait,' Viduka told a news conference on Friday.
'You always have a think about it but there were always players who were there for longer.'
Dutchman Hiddink said he had delayed naming his team until just before Saturday's kickoff, but hinted there may be some surprises in the side that lines up in Sydney.
The Australians are overwhelming favourites to win the two-leg tie and Hiddink said he wanted to use the two matches as part of his planning for the next stage.
The Oceania winner will play off against the fifth-placed South American team in November for a spot in next year's World Cup finals in Germany.
'Winning is the key but maybe we are thinking in two blocks,' Hiddink said.
'Everyone is saying it's (going to be) easy... but I don't want to underestimate them or be disrespectful of the opponents.'
Australia have qualified for the World Cup finals just once, in 1974. They have won the Oceania title on the last four occasions only to be beaten in playoffs by Scotland (1990), Argentina (1994), Iran (1998) and Uruguay (2002).
'My dream ever since I was a little boy was to play in the World Cup and getting there would be the highlight of my career, that's motivation enough,' Viduka said.
'I think a lot of the players also realise that we want it badly and this time round it's got a different feel to it.'
Hiddink took South Korea to the semi-finals at the last World Cup but said he doesn't feel any extra responsibility to end Australia's long World Cup drought.
'Pressure is part of our job but it's how you cope with it,' he said.
'It's always a challenge but pressure has never affected me in a negative way.'
Solomon Islands surprised everyone by reaching the Oceania final ahead of New Zealand but their Brazilian coach Ayrton Andrioli said they faced a near impossible task beating the Australians after having less than a month to prepare together.
'We're not kidding ourselves, we know the task, how difficult it will be,' Andrioli said.
'They did not prepare the way they should and the players are not exposed or used to this kind of occasion, so we've been trying to make sure they are focused and able to concentrate.
'They will have to play the game of their lives, because this is the biggest game they've ever played.'
Solomon Islands will host Australia in the return leg in Honiara on Tuesday.