He's been a little off colour since his tax problems of last year but Lionel Messi remains arguably the greatest player in the world – although Cristiano Ronaldo and his fans would have something to say about that.

Messi's Argentina are favourites for this group, having led the South American charge through qualifying. However, it won't be easy: tournament debutants Bosnia-Herzegovina and African champions Nigeria will push them hard.

Bosnia are led by strikers Edin Dzeko and Vedad Ibisevic, Bosnia bagged 30 goals in qualifying, while Nigeria won this year's Africa Cup of Nations and impressed in a recent 2-2 friendly draw with Italy.

Iran are the best team from the Asia qualifying, but they are unlikely to make much of an impression.

The big argument is expected to be over who finishes second to Argentina.

• Argentina

Manager: Alejandro Sabella

Star player: Lionel Messi

Previous record: Winners 78, 86

Summary: Can Messi cope with the enormous pressure on his shoulders? Argentina are perhaps living on the memories of the 80s – lost the 1990 final and

since then they have been unable to progress beyond the quarter-finals.

• Iran

Manager: Carlos Queiroz

Star player: Javad Nekounam

Previous record: Group stages

Summary: Long gone are the days of Ali Daei, Karim Bagheri and Mehdi Mahdavikia. This could be a real struggle for Iran, even under the watchful eyes of their ex-Portugal and Manchester United coach.

• Bosnia-Herzegovina

Manager: Safet Susic

Star player: Edin Dzeko

Previous record: N/A

Summary: Their first World Cup finals – and they could be a surprise package. They are strong all the way through the team – goals up front, tight at the back. Plenty of players with top European league experience.

• Nigeria

Manager: Stephen Keshi

Star player: John Obi Mikel

Previous record: Rd of 16

Summary: Their reputation has taken a bit of a battering since the 1990s, but coach Keshi has a tough streak and isn't fooled by reputations. Won the Africa Cup of Nations last year and will be optimistic of going through.