The CFL slapped Isaac with a one-game suspension Monday for delivering a helmet-to-helmet hit on Saskatchewan Roughriders quarterback Darian Durant on Saturday night.
Isaac wasn't penalized on the play.
The suspension came following a hearing earlier Monday between Isaac and CFL commissioner Mark Cohon.
This marks the third time the CFL has disciplined Isaac this season.
He was fined both previous times, the first for an illegal hit on Calgary Stampeders tailback Jon Cornish on Aug. 18.
Isaac received a second fine for a helmet-to-helmet blow against Winnipeg quarterback Buck Pierce on Sept. 29 that left Pierce with a mild concussion.
Toronto cemented second place in the East Division standings with a 31-26 road win over Saskatchewan and will cap its regular season hosting the Hamilton Tiger-Cats on Thursday at Rogers Centre.
The Argos said in a statement they expect Isaac will serve the suspension and sit out Thursday's game.
Under CFL rules, he has the right to appeal the suspension and send the matter to an independent arbitrator for consideration.
That would allow Isaac to play Thursday but potentially miss the Argos' playoff game should the arbitrator reject the appeal.
In the fourth quarter Saturday, a blitzing Isaac ran in untouched towards Durant, who was facing the opposite direction and looking downfield to pass.
As he proceeded to hit Durant, Isaac's helmet made contact with the Rider quarterback's helmet, forcing Durant to fumble but it was recovered by Saskatchewan running back Kory Sheets.
No penalty was called on the play.
It's the second time this season the CFL has issued a suspension.
The league gave B.C. Lions defensive lineman Khalif Mitchell a two-game ban for bending the arm of Edmonton Eskimos offensive lineman in a game July 20.
Mitchell appealed the suspension but it was later upheld by an arbitrator.