Lionel Messi left the Maracana with a smile on his face following his man of the match performance against Bosnia-Herzegovina.

"We have things we need to improve but it was a good first game at the World Cup," the 26-year-old captain said after setting up Argentina's first goal and then scoring the decisive second after a stunning burst from midfield.

"Everyone was anxious to do well. The result was the most important," he added, before admitting that a half-time tactical tweak by coach Alejandro Sabella proved crucial in helping him flourish after the restart.

Argentina switched from a system with three central defenders to their customary 4-3-3, with Gonzalo Higuain joining the attack and helping set up Messi's goal.

"I think it was a great second half. We had the ball, created chances. That is how we need to carry on, playing the way we did in the second half.

"The important thing is that we started well, but the system (in the second half) for us strikers obviously is better because we have more chances to hit them on the break and more options for the pass when we bring the ball out.

"It favours us strikers I think. We struggled a bit in the first half and had possession too far away from their goal. It was difficult, but we used the two systems and we won the game, which is the most important thing."

The Barcelona superstar was also impressed with the atmosphere generated by the large Argentinian contingent in the Maracana crowd of close to 75,000.

"The stadium is impressive and it was great to see so many Argentinians, which I'm sure will be the same in Belo Horizonte and Porto Alegre. It was a great atmosphere and it makes me proud," he said.

Argentina take on Iran in Belo Horizonte next Saturday, June 21, before facing Nigeria in their final Group F game in Porto Alegre on June 25