Tailback Chad Kackert will miss the game at B.C. Place due to a leg ailment.
He sustained the injury in last weekend's 45-31 home win over Hamilton, a game that saw Kackert rush for a career-high 172 yards and three touchdowns.
Kackert didn't make the trip to Vancouver with the Argos.
Rookie Gerald Riggs Jr. will replace Kackert in the backfield.
Riggs is the son of Gerald Riggs Sr., a former NFL running back who was a three-time Pro Bowl selection over 10 seasons with the Atlanta Falcons and Washington Redskins.
Kackert's absence is a blow to Toronto (6-4) as the defending Grey Cup-champion Lions (7-3) sport the CFL's stingiest defence.