Montreal quarterback Johnny Manziel has been placed under the CFL's concussion protocol and is unlikely to play when the Alouettes visit Edmonton on Saturday.
Manziel was rocked by a hit while trying to run the ball over the goal-line in a 24-17 loss in Ottawa last weekend in his second career CFL start.
The uncertain status of the one-time Heisman Trophy winner means unheralded Antonio Pipkin will likely start under centre for the Alouettes.
A statement from the team suggests Manziel felt symptoms which could be associated with the prescribed medication he uses for a previously diagnosed medical condition.
He missed practice in order to have some blood work done.
The team says he'll be under close observation and that his situation will be re-assessed in the coming days.