Lionel Messi remained at the heart of an injury scare only weeks before the World Cup after medical tests diagnosed him with muscle fatigue in his left hamstring, Inter Miami announced on Monday.

The Major League Soccer club's update provided no clear timetable for the Argentine superstar's return after his abrupt exit from Miami's 6-4 victory over Philadelphia in the 73rd minute on Sunday.

The 38-year-old icon for the defending World Cup champions grabbed the back of his left leg and asked to come off, but appeared to be walking normally as he made his exit to the locker room.

"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 statement.

"The timeline for his return to physical activity will depend on his clinical and functional progress."

That gave precious little indication about the status of the eight-time Ballon D'Or winner as Argentina prepares to defend the crown in a World Cup co-hosted by the United States, Canada and Mexico that kicks off June 11.

Argentina's first match will be five days later against Algeria in Kansas City.

Messi has managed his workload since joining Inter Miami in 2023, with team staff regularly excusing him from matches in congested fixture periods.

MLS has started a break for the World Cup.

Messi captained Argentina to their third World Cup title in Qatar in 2022 and is expected to lead the team again in what could be his record-matching sixth appearance at the tournament.

Argentina's squad is due to be named next week and the South American giants will journey to the United States for pre-World Cup friendlies against Honduras on June 6 and Iceland on June 9.