Lionel Messi exited Inter Miami's final club match before the World Cup with muscular fatigue. The 73rd-minute substitution sparked an injury scare, but coach Guillermo Hoyos stated it was purely a precautionary measure after playing on a heavy pitch.

The eight-times Ballon d'Or winner was substituted after clutching the back of his thigh in the wake of one of his trademark free kicks during Inter's 6-4 win over the Philadelphia Union in Miami.

"We don't have a medical report on that yet, but we will have one shortly," Hoyos told reporters when asked why the talismanic forward was taken off.

"He was genuinely suffering from fatigue in that regard; it is indeed fatigue. He was tired, the pitch was heavy and when in doubt, the standard approach is always to ensure you don't take any risks."

No preliminary diagnosis of any issue for Messi was immediately announced. Messi has dealt with hamstring issues at least two other times during his three-year stint with Inter Miami.

Messi had two assists and Germán Berterame scored twice during a record-setting first half for Inter Miami. But Messi basically took himself out of play and reached toward his left hamstring at least once, then didn't even venture toward the Inter Miami bench when he could be subbed out.

Messi was replaced by Mateo Silvetti, then left immediately through the tunnel connecting the field with the team's locker room. Messi was walking under his own power, albeit slowly, and without any team medical personnel with him.

Heavy rain began falling early in the second half, causing some players to seem to slip on the turf. It wasn't clear if Messi's departure was precautionary or not, and it didn't seem like he took any major missteps during the worst of the rain.

Messi has said in the past that he would only play in the World Cup if healthy. Argentina starts group stage play on June 16.

Major League Soccer is now taking a mid-season break for the World Cup, which will be co-hosted by the United States, Canada and Mexico from June 11 to July 19.

Argentina coach Lionel Scaloni announced a 55-man squad, including Messi, on May 11. He will need to reduce it to 26 before FIFA's June 1 deadline.

Messi was highly influential as Argentina won the World Cup for a third time in Qatar four years ago. They open their title defence against Algeria in Kansas City on June 16.