Inter Miami CF said Monday that Lionel Messi suffered from muscle fatigue in his left hamstring during Sunday's win over the Philadelphia Union, forcing him to leave the game in the 73rd minute.
"After undergoing further medical tests this Monday, the initial diagnosis indicates an overload associated with muscle fatigue in his left hamstring," Inter Miami said in a news release. "The timeline for his return to physical activity will depend on his clinical and functional progress."
The Miami captain asked to be substituted after taking a free kick in the team's final game before the World Cup break.
Messi was seen grabbing at the upper part of his left thigh before requesting the substitution and heading directly into the locker room. He was replaced by Mateo Silvetti.
Messi did not require any assistance as he left the field.
The game was tied 4-4 when Messi left the field, but Miami scored a pair of goals after his exit to win the game and go into Major League Soccer's extended break during the World Cup in second place in the Eastern Conference.
"As far as I know, we don't have a report on that yet, but he really was fatigued. It was fatigue," Miami coach Guillermo Hoyos said after the game. "Yes, it was fatigue. He was tired, the field was heavy, and rather than doubt, you always say not to take the risk."
The Argentina national team is set to face Algeria, Austria and Jordan in Group J of the World Cup. It will also play two pre-tournament friendlies against Honduras on June 6, and Iceland on June 9.
The defending champion will kick off the summer tournament on June 16 against Algeria in Kansas City, Missouri. Manager Lionel Scaloni has not announced his 26-player World Cup roster.
Messi has already appeared in five World Cups, winning the Golden Ball as the tournament's best player twice -- first in 2014, then again in 2022 when he led Argentina to the title. That award has been given out only since 1982, but he is the lone player to win it twice.