The forward scored what proved to be the decisive goal in La Albiceleste's 2-1 victory over Bosnia & Herzegovina, with Alejandro Sabella changing his tactics at half-time
Alejandro Sabella started with a 5-3-2 formation and saw his side take the lead in the early exchanges when Sead Kolasinac scored an own goal, but they struggled for the rest of the half and a tactical switch was made at the break.
La Celeste performed better in the second half and Messi picked up his second World Cup goal before Vedad Ibisevic pulled one back, and the Barcelona man was realistic about the performance.
"It's normal to have doubts. It's the first match, we were nervous, anxious. That's what you get when you make your debut," he told reporters. "The most important thing was winning and we did it. Bosnia are a great team but we still have things to improve.
"We let them play in the first half, we gave them the ball and it was very hard for us to make it to their goal because we were very far away.
"The [second] goal was a big relief for all of us because the match was getting harder. It was also special for me, and to score at the end of the game was very good.
"The system [in the second half] for us [attackers], we like it better. We have better possibilities of attacking and when we go forward we have more possibilities of passing and scoring. We’re favoured by this line-up.
[In the first half] I was alone and Kun was alone and it was difficult, but we used both systems, we won and it was important to win the first match."Thousands of Argentina fans filled the Maracana stadium in Rio de Janeiro for the match, and greeted Messi with loud cheers when he walked out on the pitch.
The No.10 had no doubts about his country's support, and insists he is focusing on winning the trophy back in the same stadium on July 13.
"It was incredible how the people cheered for us. We know it's going to be like this in Belo Horizonte too and even more in Porto Alegre. We have to keep going, take it easy, be cool and follow our dream."
Sabella was also pleased to get the points on the board but admitted he made a mistake with his tactics and personnel.
"I'm happy with the result and with how we played in some periods of the game. But it's also true that we failed in some parts, partly because of my mistakes.
"It was a hard, close game but we improved in the second half when Higuaín came on. The 2-0 was too much for how we played, I think the 2-1 was a fair result."