League sources told ESPN and NFL Media that Fitzpatrick tested positive for the coronavirus, meaning he will be unavailable to play in Sunday's regular-season finale against the division rival Buffalo Bills.
The Dolphins announced Fitzpatrick's placement on the COVID-19 list on Thursday but didn't confirm if he tested positive for the virus. He was a full participant in Wednesday's practice, indicating that the positive test resulted from recent exposure.
Dolphins safety Eric Rowe said that head coach Brian Flores revealed Fitzpatrick's status during a Zoom meeting.
"It hurts. He's a leader on our team. He brings energy," Rowe said. "I'm sure it's worse for him because he loves the game and no one wants to catch COVID. With that, you have to push forward.
"COVID is a real-deal thing whether you don't have symptoms or you do. Just praying he doesn't have symptoms or he didn't pass it to his kids."
Rookie Tua Tagovailoa is the Dolphins' starting quarterback, but the 38-year-old Fitzpatrick has served in what Flores calls a "ninth-inning reliever" role. Last week, Fitzpatrick led the Dolphins to a 26-25 comeback win over the Las Vegas Raiders in relief of Tagovailoa.
The Dolphins signed Jake Rudock to the 53-man roster Thursday. He is expected to serve as Tagovailoa's backup Sunday.
Earlier Thursday, the Cleveland Browns shut down their practice facility for a second straight day to conduct contact tracing after two more players tested positive for COVID-19.
Browns star cornerback Denzel Ward and linebacker Malcolm Smith were the two players who tested positive for the virus, according to multiple reports. The team added Ward and Smith to the reserve/COVID-19 list on Thursday.
"The Cleveland Browns were informed of two additional positive COVID-19 test results among our players this morning," the team said in a statement. "The Browns facility is currently closed while contact tracing is conducted to identify any high-risk close contacts.
"The team will continue to work remotely this morning while following the NFL-NFLPA intensive protocols as the health and safety of our team, staff and the entire community remains our highest priority."
The Browns also closed their facility Wednesday after a coach and a practice squad player tested positive for the coronavirus. On Tuesday, the team placed tight end Harrison Bryant and safeties Karl Joseph and Andrew Sendejo on the COVID-19 list.
Meanwhile, the Browns activated receivers Jarvis Landry, Rashard Higgins, Donovan Peoples-Jones and KhaDarel Hodge and starting linebacker Jacob Phillips off the COVID-19 list.
Cleveland can clinch its first playoff berth in 17 seasons with a win over the Pittsburgh Steelers on Sunday.