Home favourites Australia and in-form South Africa will pose the biggest threat to India's title defence as they seek to assert their supremacy in cricket's showpiece event, the ICC World Cup, which gets rolling with a double header in Melbourne and Christchurch tomorrow. Besides the top-ranked Australian side, South Africa will once again begin their quest to shed the chokers tag that they have been carrying since their re-entry into international cricket, in the 11th edition of the quadrennial extravaganza. While four-time winner Australia will be pitted against traditional rival England at the MCG, co-hosts New Zealand, still looking for an elusive triumph, will lock horns with 1996 winners Sri Lanka at Hagley Oval on the first day of the tournament. India's face-off with arch-rivals Pakistan on Sunday here will complete a bumper opening weekend. While the format chalked out by ICC is likely to ensure that all top eight teams Australia, England, South Africa, India, New Zealand, Sri Lanka, Pakistan and the West Indies get to the top-eight phase, this edition of the mega-event will have at least three teams that are on even keel as far as winning the trophy is concerned. Darren Lehmann's Australia are entertaining, in-form and on home soil. Quality and form could keep South Africa and New Zealand slightly better-placed as title contenders compared to some of the other top teams like India, who are battling injuries and inconsistent form. It will not be an easy job for Mahendra Singh Dhoni and his men to retain the Cup that they won at a packed Wankhede Stadium four years ago. A side still in transition, the Indian team's composition has undergone a sea change in the last four years with the retirement of the iconic Sachin Tendulkar and the gradual phase-out of last edition's heroes Yuvraj Singh, the supremely talented Virender Sehwag, Gautam Gambhir and Harbhajan Singh. The batting largely depends on Virat Kohli, Ajinkya Rahane, Rohit Sharma and skipper Dhoni but it's the lack of experienced bowlers that may keep the fans worried. Although India's limited overs team has done well but their recent performances in Australia will certainly keep them worried as they gear up for their first match against Pakistan in what could be Dhoni's final ODI World Cup. Australia will be keen to win a fifth World title having won the first time in the Indian sub-continent in 1987 followed by a hat-trick in 1999 (England), 2003 (South Africa) and 2007 (West Indies). The team has talented players in all department, and the only worry will be skipper Michael Clarke's hamstring injury, which ruled him out of the tournament opener. But with an in-form David Warner, Steve Smith, Glenn Maxwell ready to tear apart any bowling unit and the dangerous Mitchell Johnson leading a good bowling attack, this side is more competent than the one led by Allan Border in 1992. Warner, Smith, Maxwell, Aaron Finch and stand-in skipper George Bailey make Australia a formidable batting line-up with Shane Watson and Mitchell Marsh's all-round abilities. While Johnson's pace can be intimidating, Starc and Josh Hazlewood add variety to the attack. With wicketkeeper Brad Haddin coming in at No 8 and a fast bowler like Patrick Cummins also in contention for a berth, it will be difficult to stop the Australian side if it gets into a winning momentum. Regarding South Africa, the challenge for AB de Villiers and his men will be to get the monkey of losing the plot in the knockout rounds off their back. In skipper De Villiers, they have one of the best batsmen in contemporary cricket with the fastest ODI century under his belt. They have one of the most compact batsman in world cricket in Hashim Amla, and a brilliant finisher like David Miller. The Dale Steyn-Morne Morkel duo forms the most seasoned new ball attack in the World Cup. Wayne Parnell and Vernon Philander have variations to trouble any team. The quarter-final jinx is something that South Africa will be desperate to break this time around. For co-hosts New Zealand, this is the best opportunity to win a World Cup. Always a solid team and has been in the semi-finals on a number of occasion, the team led by Brendon McCullum will look to one better than Martin Crowe's band of 92', which had reached the semi-finals with some top showings. The batting will primarily depend on McCullum and young Kane Williamson, with Corey Anderson giving necessary impetus with his big-hitting prowess. One of the best left-arm spinners of all time, Daniel Vettori will like to make his swansong World Cup appearance a memorable one. More In Tim Southee, Trent Bolt and Grant Elliott, they have the perfect seam attack and would be playing mostly in New Zealand conditions. Sri Lanka had a moderate series in New Zealand and their knowledge about the conditions will come in handy. Mahela Jayawardene and Kumar Sangakkara walked out of the international T20 format on a high after winning the World T20 in Bangladesh last year and they won't mind a repeat in the 50-over format as well. This will be Jayawardene's last tournament in Lankan jersey and having lost two World cup finals, it would be an icing on cake for the legend. England under Eoin Morgan can't exactly be termed title contenders but they do have a good bowling attack led by the mercurial Jimmy Anderson and the ever-so effective Stuart Broad. The batting still looks a bit on the weaker side although the diminutive James Taylor is making a case for himself. West Indies are the weakest among the top eight sides and the decision to drop someone like Dwayne Bravo along with Kieron Pollard might severely affect them. Plagued by internal issues, the team led by fast bowler Jason Holder is not the best in the world although the batting unit does have quality. Chris Gayle and Dwayne Smith's destructive powers are well-known. Marlon Samuels can win big games but, on his off-day, can also be a case of self-destruction. Sunil Narine's absence will also hurt their chances, and not to forget Bravo's ability to provide brilliant variations at the death besides the runs with the willow. The minnows will have a tough time getting into the quarters in this format as it warrants consistent results and three wins. Bangladesh and Ireland are the two better-placed teams with ability to upset the big boys on their day. Shakib Al Hasan, one of world's premier all-rounders, will be back to torment the big boys after all the controversies last year, while Kevin O'Brien's 50-ball-100 against England four years ago in Bangalore is still talked about.