The six-foot-four 221-pound receiver suffered a hamstring injury in Hamilton's 16-6 home win over the Ottawa Redblacks on Friday night.
Hamilton (7-8) is tied atop the East Division standings with Montreal (7-8). They're two points ahead of Toronto (6-9), which dropped a 20-12 home decision Saturday to the Alouettes.
The Ticats and Argos meet in an important match for both teams as the winner clinches the season series 2-1.
Fantuz has a team-high 62 catches for 639 yards and three TDs.