Messi to miss Miami's MLS Orlando clash
"No, Leo will not be available tomorrow," Mascherano said. "He is fine, but obviously it would be crazy to risk taking him to Orlando because of all that is ahead.
"We are optimistic that he will soon return with us."
After the Florida Derby clash with Orlando, Inter will host the LA Galaxy on August 16 and three days later they play a Leagues Cup quarter-final against Mexico's Tigres UANL.
Messi, the eight-time Ballon d'Or winner, missed the club's last Leagues Cup group stage match after suffering the "minor muscle injury" in his upper right leg in Miami's win over Necaxa on August 2.
Inter are currently fifth in the MLS Eastern Conference, eight points behind leaders Philadelphia and a point ahead of Orlando with three matches in hand.
Despite the setback for Messi, Miami have been buoyed by the arrival of his Argentine compatriot Rodrigo De Paul, who scored his first goal for the Herons in a 3-1 victory over Pumas UNAM that clinched their Leagues Cup quarter-final berth.