Despite recording a third successive win in Group F, the Argentina boss accepted his side were still not at 100 per cent
Argentina coach Alejandro Sabella is hoping his side can marry their offensive power with greater defensive stability in the World Cup knockout stages.
Sabella's men were, not for the first time in this tournament, below their best in Wednesday's 3-2 win over Nigeria, a result which guaranteed them top spot in Group F.
Lionel Messi was again the star, twice putting Argentina ahead - his third and fourth goals in three pool matches - but defensive lapses allowed Ahmed Musa to equalise on each occasion.
Defender Marcos Rojo grabbed the winner five minutes into the second half, using his knee to divert home a left-wing corner.
“We are an offensive team and, as such, there will be some questions about the defence," Sabella said. "The defence is doing a great job, but we must study ways on how to improve it.
“If you make mistakes like that in the round of 16 you’ll be punished.”
With qualification all but secured, Sabella withdrew Messi after 63 minutes and admitted it was a pre-arranged move.
“I wanted to preserve Messi," he added. “With 3-2 on the scoreboard, I thought it would be better to do this. We talked before the match, he knew he was coming off sometime.”
Sergio Aguero was another who didn't complete the 90 minutes, limping off seven minutes before the break.
Should he miss the next game, it will leave Sabella with a decision to make.
“Now, without Aguero, we’ll have to see," he said. "There are players with the same traits, or we can use someone coming from the sides, like [Ezequiel] Lavezzi did today.
“There were 30 minutes left, and we had a chance of testing something we could use in the future. And that’s what we’ve done.”
Sabella accepts the performances have to improve generally if Argentina are to land their first World Cup title since 1986.
“There are results, and there are performances, and they don’t always walk together," he said.
“Sometimes, a coach can have good results while his team has bad performances, but we won’t dwell on that.
“I am satisfied with the qualification and what we’ve done so far, but we must look to improve.”