The Inter Miami player's double in the 2-0 win over Austria at Dallas Stadium took him to 18 World Cup goals, surpassing both Miroslav Klose's men's record of 16 and Marta's overall tournament mark of 17 to claim sole possession of the all-time record.
"When the team was having a rough time without the ball he worked, he managed to steal the ball," Scaloni said of his former teammate. "You could see his level of commitment.
"There's a reason for that, he has commitment and this is what he generates. I have no more words to talk about Leo. It makes us a little bit tired talking about him all the time."
Messi suffered one blot on his performance with an eighth-minute penalty miss but when he opened the scoring half an hour later the goal allowed him to move clear of Klose as the World Cup's most successful striker.
Despite only holding a one-goal lead, Argentina were rarely troubled, with goalkeeper Emi Martinez making one save of note before Messi's determination secured his second goal five minutes into stoppage time.
"It had been complex," Scaloni said of the challenge presented by Ralf Rangnick's side. "We had the peace of mind we needed toward the end. I'm so happy with Leo's performance, he scored again when we are suffering.
"The team did suffer today, at times they were creating difficulties and we didn't have possession. We know how to suffer and that's something praiseworthy as a team.
"The team knows how to behave at all times. This was an opponent that had very tall players, that posed a challenge. No one thought this would be easy. The two matches we have had so far have been complex."
Back-to-back wins in Group J have already confirmed Argentina's progress into the knockout rounds and Scaloni remains confident the defending champions will be contenders at the business end of the tournament.
"This World Cup has nothing to do with playing favourites or the players in the national teams," he said. "There are other elements at play, the levels of fitness, the emotional element.
"There are so many teams that can win, one of the big ones will win. We will be there, we will be one of the contenders, but it will be hard facing one of these big teams.
"But it will be hard for them facing us."
FIFA World Cup 2026
The 2026 World Cup is taking place from June 11th to July 19th in the United States, Canada and Mexico. The tournament features 48 national teams and is played at 16 modern stadiums.
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