Manchester City striker Sergio Aguero suffered a hamstring injury while playing for Argentina in the 2-0 World Cup qualifying defeat by Ecuador.
Aguero, who scored five goals in City's win against Newcastle on 3 October, was carried off after 22 minutes.
The 27-year-old is set to have a scan and looks likely to miss Argentina's game against Paraguay next week.
Aguero had only just returned to fitness after a knee injury earlier in the season.
A statement on the City website said: "The striker pulled up holding his left hamstring while chasing a long ball downfield."
The Premier League leaders are next in action against Bournemouth on 17 October.
Elsewhere in South America, Brazil were beaten 2-0 by Chile in their World Cup qualifier, with Arsenal's Alexis Sanchez and Eduardo Vargas scoring the goals.