PSG and Argentine star Lionel Messi (AFP)
The six-time Ballon d'Or winner missed the last two matches with his club Paris Saint-Germain due to knee and hamstring issues.
He had been expected to miss Friday's crunch clash against neighbors Uruguay but now appears to be fit to play.
"Messi is in good shape and if that continues he will play," said Scaloni.
"In principle, he's available. If he's in good shape you already know what I think about his game and his status in the team.
"We will take the final decision this (Thursday) afternoon."
Argentina were due to train at their base on the outskirts of Buenos Aires on Thursday afternoon before traveling to Uruguay.
When Messi linked up with his national team on Monday he was training apart but he joined his teammates on Wednesday.
"It's easy to live with Messi, who always wants to play, because I also want him to always play," said Scaloni.
Argentina sit second in the single South American World Cup qualifying table, six points behind runaway leaders Brazil but nine points ahead of Uruguay, the highest placed side outside the automatic qualification sports.
Scaloni's team are on a 25-match unbeaten run and lifted the Copa America in July, beating Brazil 1-0 in the final at Rio de Janeiro's iconic Maracana stadium.
It was Messi's first ever major title with his country having lost the 2014 World Cup final and three Copa America finals prior to that.
Following their trip to Uruguay, Argentina will host Brazil in San Juan on Tuesday.
(For more sports news and updates, follow Ahram Online Sports on Twitter at @AO_Sports and on Facebook at AhramOnlineSports.)