Messi missed two matches due to a knee injury before returning for Paris Saint-Germain in their Champions League win over Manchester City and last week's shock Ligue 1 loss at Rennes.
The six-time Ballon d'Or winner is away on international duty with Argentina, who will visit Paraguay on Thursday, and Messi has been given the all-clear to play.
"Messi trained with us yesterday [Tuesday] without any problems and this morning too, so he's fine to play," Scaloni told reporters on Wednesday.
"Which is the most important thing and he's like the rest of the group, wanting to get together and do the best for the national team. Regarding his injury, it is evident that he has played two games before coming here and this is fine."