With the Albiceleste wrapping up their spot in the next round thanks to a perfect group stage record, their star forward vowed that there is still more to come
La Albiceleste defeated Nigeria 3-2 to finish top the group with wins in all three games, meaning they will face Switzerland in the next round.
Messi, who scored twice against the African side to take his tournament tally to four, did not hide his desire for the team to step up its performance level as the competition enters its tougher phase.
"We saw a good Argentina, despite the two Nigerian goals. Now we want more, we have to keep improving," he said to reporters.
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"I think we have improved from the last [two] games. We played against a team that was going forward with good players.
"We said before: our strikers had to move a little bit more because we weren't finding spaces. We had that today and we have to work, so the next game we won't concede goals."
The Barcelona forward also revealed that he was enjoying the atmosphere surrounding the tournament, as he bids to lead Argentina to its first World Cup trophy since 1986.
"It's great to see so many people here. We were expecting it and in the previous games it was like that," he continued.
"It's beautiful what we're living through these days, I hope we can keep giving them joy.
"It's a strange World Cup, with results we weren't expecting to see. We have to keep calm. We're still behind our dream, the dream we all want."
Messi scored four of Argentina’s six goals in the group stages and will be expected to lead his side out for its round of 16 fixture on July 1.