Messi, who had gone back on his decision to quit the team following their Copa America final defeat in June, scored the only goal in a 1-0 home win over Uruguay on Thursday that sent Argentina to the top of the South American group.
However, the Argentina captain said he had a groin pain and had to think about his fitness at the start of a busy season for his national side and his club Barcelona.
“My groin is hurting a lot, from before this match,” Messi told reporters. “We’ll see, I always want to be (in the team) but there are also a lot of important matches coming up.”
Messi explained why he had said he was retiring from international football after Argentina’s loss to Chile in New Jersey in which he missed his team’s first penalty in the decisive shootout.
“I didn’t deceive anyone in that moment,” he said. “I was very disappointed because it was a hard blow and I said that because that’s what I felt.
“But afterwards, seeing what this group (of players) is like, and with the affection of the fans, I reconsidered.”
It was Messi’s third defeat in a major final with Argentina in two years including the 2014 World Cup final against Germany in Brazil, and fourth altogether.
Messi is now back gunning for a fourth World Cup appearance in Russia in 2018 with Argentina heading the 10-nation group with 14 points from seven matches.
The top four qualify for the tournament in Russia while the fifth-placed team will go into an inter-continental playoff for another place in the finals.
