Colombo: Languishing at the bottom half of the ranking table, Australia would like to start their World Twenty20 campaign on a positive note when they take on âgiant killersâ Ireland in their tournament opener here on Wednesday.Australia has so far failed to tame the shortest format of the game and it will be a test of their character when they face William Porterfield-led Irish side, who are well known to spring a few surprises at the big stage.Though, they have just one victory to their credit against an ICC Full Member side in the T20, their unpredictability can well be gouged by a thumping win over England in the 50-over World Cup last year in Bangalore.Irelandâs World Cup triumph over Pakistan in 2007 World Cup in the Caribbean is yet another example of their ability to surprise big teams. The Irish men have won both their warm-up matches in the build up to the championship and interestingly, they were also briefly ahead of Australia on the ranking list earlier this month, something that Kangaroos will be wary of.Having lost to minnows Zimbabwe in the same championship in 2007 and being bundled out at the group stage in the 2009 edition, Australia will have a tough task at hands on Wednesday.âI will only rest easy when that gameâs (against Ireland) passed,â Australiaâs coach, Mickey Arthur, said.âThatâs not through fear of failure. They have been a giant-killer and theyâre playing with a quite nice bit of freedom. Any team in this competition can win if they have a good day,â he added.Australia warmed-up for the campaign with a comprehensive win over New Zealand, but their nine-run loss to defending champions England in their second warm-up match, courtesy to some wayward bowling from their speedsters, would be a cause of worry for skipper George Bailey.Bailey would definitely like the young quicks in Mitchell Starc and Pat Cummins to be more disciplined and he would also expect a better show with the ball from experienced Shane Watson and Daniel Christian.With Xavier Doherty unavailable for the first match, Australia will bank on the slow left-arm chinaman of Brad Hogg to put curbs on Irish scoring.With Watson and David Warner opening the innings and Michael Hussey and Bailey leading the middle-order, Australian batting line-up certainly exhibits a settled look but the absence of their most experienced T20 campaigner in David Hussey is still debatable.The younger Hussey has been sidelined from the team following a streak of poor performances. His inability to finish matches in recent past has only added to his woes.The 35-year-old veteran of 189 T20 games has been replaced with young Glenn Maxwell. The Victorian allrounder has shown a lot of promise, but it remains to be seen whether he is able to fill the big shoes of David Hussey or not.Irish batsmen, on the other hand, have been in good nick with opener Paul Stirling leading the charge with a quick-fire 71 off just 41 balls against Bangladesh and experienced Neil O'Brien coming good against Zimbabwe.Ireland also boasts of big hitting Kevin O'Brien, who registered the fastest ODI century in the 2011 World Cup to see his team through against England. The team will further be buoyed by the presence of left-arm spinner George Dockrell, who was recently adjudged the Associate Player of year 2011.The Irish quicks will, however, be led by experienced Boyd Rankin along with Alex Cusack. Porterfield may also play veteran Trent Johnston to add solidity to the side.Probable XIs:Australia: 1 George Bailey (C), 2 Shane Watson, 3 Daniel Christian, 4 Pat Cummins, 5 Ben Hilfenhaus, 6 Brad Hogg, 7 Michael Hussey, 8 Glenn Maxwell, 9 Matthew Wade (WK), 10 David Warner, 11 Cameron White.Ireland: 1 William Porterfield (C), 2 Alex Cusack, 3 George Dockrell, 4 Trent Johnston, 5 Nigel Jones, 6 Tim Murtagh, 7 Kevin O'Brien, 8 Niall O'Brien (WK), 9 Boyd Rankin, 10 Stuart Thompson, 11 Andrew White.