ESPN, which cited a National Football League (NFL) source, said the neurotrauma consultant made "several mistakes" while evaluating Tagovailoa, who seemed to exhibit concussion symptoms after hitting his head on the ground during Sunday's game.
The source said the NFL Players Association opted to exercise its right to dismiss the doctor as part of an agreement with the league to fire an unaffiliated neurotrauma consultant without agreement from the other party.
Tagovailoa was cleared to remain in the game and four days later against the Cincinnati Bengals was taken off the field on a stretcher after he again hit the back of his head on the ground when he was chased down and thrown to the turf.
The Dolphins' quarterback's arms appeared to seize up almost immediately after the hit on Thursday and he remained on the field for about seven minutes before being taken to hospital where he was diagnosed with a concussion.
The NFLPA initiated an investigation into the handling of Tagovailoa's concussion evaluation during Sunday's game and the sequence of events has raised questions about the NFL's concussion protocols.
The NFL and NFLPA issued a joint statement later on Saturday.
"The NFL and the NFLPA agree that modifications to the Concussion Protocol are needed to enhance player safety," they said.
"The NFLPA's Mackey-White Health & Safety Committee and the NFL's Head Neck and Spine Committee have already begun conversations around the use of the term 'Gross Motor Instability'.
"We anticipate changes to the protocol being made in the coming days based on what has been learned thus far in the review process."