"If you knew the way that he played in the Copa America you'd love him even more," Scaloni told reporters after Argentina's 1-0 win at the Maracana stadium in Rio de Janeiro.
"You can never do without a player like him, even when he is not fully fit like in this game and the previous one."
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Scaloni did not say what the injury was but he showered Messi with praise on a night Argentines took to the streets in huge numbers to celebrate their first international title in 28 years and Messi's first victory with the national side.
Messi, winner of the FIFA Player of the Year award a record six times, has won every club and individual honour with Barcelona but he had lost all four of his previous finals with Argentina.
The 34-year-old had shown his frustration with the defeats, retiring after losing the 2016 Copa America to Chile only to return to the international fold a few weeks later.
"In the end he did not throw in the towel and he succeeded," Scaloni added.
"We are talking about the best footballer of all time and everyone knew how important it was for him to win a title with the national team.
"I have a relationship that is different than the [usual] coach-player relationship. We greet each other, we hug each other, and I am eternally grateful to him and his teammates."