Tua Tagovailoa is officially ruled out from the Sunday's week 17 match against New England Patriots.
After suffering a head injury during this past weekend's loss to the Green Bay Packers, Tua was put under concussion protocol on Monday.
He has been in the concussion protocol twice this season.
Tua's prior history of head injuries makes this concussion particularly worrisome for him.
During a Week 4 game against the Cincinnati Bengals, the Miami quarterback sustained a terrible head injury.
He looked to sustain another severe head injury just a few weeks earlier in Week 3, but the Dolphins allowed him to play.
With Tua's most recent head injury, Miami is undoubtedly exercising additional caution, especially in light of the harsh criticism the team received for how it handled Tua's earlier head injuries.
Teddy Bridgewater, the Dolphins' backup quarterback, is expected to start this weekend.
Miami has lost each of its last four games after beginning the season with an 8-3 record. To ensure their place in this year's postseason, the Dolphins must win out.