A promising season for Tagovailoa and the Dolphins has been rocked by repeated concussion concerns.
Tagovailoa hit his head against the ground twice in the same week in September, but only the second incident was logged as a concussion as he left a defeat to the Cincinnati Bengals. The first hit, against the Bills in Week 3, was described as a back issue.
The former Alabama QB missed two games then before returning, only to suffer another concussion against the Green Bay Packers on Christmas Day – one that was not identified until the following day.
Tagovailoa has not played since and will not line up against the Bills in this week's Wild Card round matchup.
Coach Mike McDaniel confirmed Tagovailoa was out, while the Dolphins are now preparing for Thompson to start as Teddy Bridgewater also remains sidelined after dislocating a finger.
Thompson's first NFL start was in Week 6, with Tagovailoa still out and backup Bridgewater also dealing with a concussion. The rookie left the game with a thumb injury.
He had to wait until Week 18 for both Tagovailoa and Bridgewater to be out again ahead of a crucial meeting with the New York Jets.
After five straight defeats, Thompson helped the Dolphins edge to a narrow 11-6 win that booked their place in the postseason, teeing up another meeting with AFC East rivals the Bills, against whom the seventh-round pick is again set to start.