Croatia pulled off a thrilling 2-1 upset win over three-time champions Italy on Saturday, making the prospect of Group G hard to predict.
Italy, Croatia and Mexico have three points apiece with Ecuadorplacing last without a win.
After a lackluster first half, three goals were scored in the action-packed second half while Italy's two goal were disallowed by a linesman and another by Franscesco Totti denied by woodwork.
It was the Italians' first World Cup finals defeat in regulation time since 1994.
Italy thought they had hit an injury time equalizer but the goal was nullified by the linesman, apparently for a foul by Filippo Inzaghi.
Christian Vieri had put Italy 1-0 ahead with a powerful header on a Cristiano Doni's cross just after the Inter Milan striker's goal was controversially ruled out.
Substitute Ivica Olic pulled the Croats even in the 73rd minutebefore Milan Rapaic shocked the Italians with a curling shot into a far corner four minutes later.
Italy created several chances in the last 10 minutes. The best opportunity came in the 87th minute as Totti's free kick hit the left post, bounding just off the goalline.
The two European teams have met four times in recent years, with both teams winning a game and drawing two. The Italians last beat Croatia in a 1942 friendly while Croatia defeated the World Cup favorites during a European Championship qualifier in 1994.
Italy looked lethargic in the beginning, managing only two shots on goal against Croatia's seven in the first half.
In the 15th minute, Cristiano Doni had a chance to put Italy ahead, beating Robert Kovac, but his shot was denied by goalkeeperStipe Pletikosa.
Croatia countered with three shots within four minutes, the most serious a Davor Vrugineric blast that was cleared off the line.