After a 2-1 victory over Bosnia-Herzegovina, Lionel Messi still insists that his team still has to do "much to improve.
The 26-year-old Argentina captain, who netted the second goal on Sunday, said the three points were the most important accomplishment in the Group F opener - and not his second World Cup goal.
"It's important to win, but we have to improve," the Barcelona star said. "It's not easy because during the first World Cup match you are always anxious and nervous, but we played a great second half and we have to keep it up that way.
Messi also acknowledged the changes from a 5-3-2 to a 4-3-3 formation made it much easier for him and fellow striker Sergio Aguero.
"I was often on my own and so was Kun [Aguero] and it was very difficult, so there are things to be improved on," he said.
"We forwards prefer the system we used in the second half, with more attacking, because we could go out against them with more passing options, although in truth, sometimes we suffer a little more," he said. "The first half cost us more because we were behind but what is important is that we won. There are a lot of things we must improve, but I am happy that we began with three points."
Argentina will face Iran in their second group game.