Yet there was a moment midway through the first half that must have struck fear into all Argentines, when Messi appeared clutch his left hamstring and rub it.
Was Argentina's superstar going to have to come off? No such luck for Croatia.
Messi was soon toying with his opponents in a way only he can and put Argentina ahead by lifting his penalty into the top corner after Alvarez was taken out by Dominik Livakovic after clipping the ball past Croatia's goalkeeper.
Alvarez poked home his first goal at the end of a surging run from halfway, starting with Messi's short pass. He put in the third following more outrageous skill from his teammate near the right corner that left Josko Gvardiol - one of the best defenders at the World Cup - grasping at thin air.
It was one game too far for Croatia, which had beaten Japan and Brazil on penalties in the knockout stage, and star midfielder Luka Modric, who - at 37 - has likely played his final World Cup match.
Summing up a frustrating game for the little midfield magician, he was substituted in the 81st minute and had a bright red nose after the ball slammed in his face moments earlier.
Argentina maintained its record of never having lost in the World Cup semifinals and has reached the final for the sixth time.Those dark days after losing to Saudi Arabia in its opening group match seem so long ago now for Argentina, which will be hard to stop in the final with Messi playing this well.
"Even though we lost our first match, we were confident that this group was going to push forward," Messi said. "We know what we are, and we called on the fans to believe in us."
MESSI RECORDS
Messi became Argentina's record scorer at World Cups with his third penalty of the tournament taking him to 11 goals in total - one more than Gabriel Batistuta. He also tied the record for most appearances at the World Cup by playing for the 25th time, the same number as Lothar Matthaus of Germany.
ALVAREZ
The 22-year-old Alvarez didn't start the tournament as Argentina's striker. He only took the place of Lautaro Martinez in the third group game and now has four goals, one behind Messi and Mbappe. He is the youngest player to score twice in a World Cup semifinal match since a 17-year-old Pele scored a hat trick in 1958.
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