The Barcelona star had only previously scored one goal in previous finals but has netted four times in just three games in Brazil so far, with a round-of-16 clash with Switzerland to come on Tuesday.
Sabella argues that it is a return to form that he, Messi himself, and the rest of Argentina had seen coming.
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Parallels have been drawn between the influence of Messi on Argentina and Barcelona colleague Neymar's effect on Brazil, while the legacy left by Diego Maradona in leading the Albiceleste to glory in 1986 also draws comparisons, but Sabella feels that it is natural for successful teams to be built around such outstanding talents.
"I think both Messi and Neymar are amazing players. Messi is the best in the world and Neymar is a great player and, with players like those, it's normal that teams depend on them," he remarked.
"Maradona was a very important player to the team in 1986 and Messi is very important to us now."
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The 59-year-old opined: "We're improving. The last match [against Nigeria] deserved a mark of seven [out of 10], since I know you like ratings, but maths is not everything.
"The team is very spirited. We're all positive but it's true this is a different phase and mistakes are not acceptable. You can make mistakes in the first phase but we know we have to keep focused and stay balanced. There are two reasons for that. We cannot go back and mistakes are not acceptable at this stage."