Scans taken on Monday confirmed that Mata sustained a fracture during the first half of Melbourne Victory's 1-0 loss to Wellington Phoenix at the weekend.
A timeline for Mata's recovery has not yet been established by the club, with discussions to take place regarding potential surgery.
“It is disappointing to be without Juan through injury, but our priority as Melbourne Victory is supporting his recovery in every way we can," head coach Arthur Diles said in a brief club statement on Tuesday afternoon.
"We remain hopeful of him rejoining the team during the 2025/26 season.”
Whether or not Mata is able to return for the Victory's finals campaign, which is set to begin on the first weekend of May, the Spanish legend has almost certainly already sewn up the A-League's esteemed Johnny Warren Medal for the most valuable player of the season, having recorded five goals and 13 assists in his 23 appearances.
15 of those 18 goal contributions came this calendar year, which saw him crowned as the competition's Player of the Month for both January and March.