Cleveland Browns quarterback Baker Mayfield has tested positive for COVID-19, sources told ESPN's Field Yates, Kimberley Martin and Adam Schefter, jeopardizing his availability for Saturday's game against the Las Vegas Raiders.

The Browns also announced Wednesday that head coach Kevin Stefanski tested positive for the virus. If Mayfield and Stefanski don't turn in two negative tests by Saturday, they will both miss Cleveland's crucial game against Las Vegas.

A source told Schefter that Mayfield feels "completely normal" despite the positive test. Case Keenum would be in line to start if Mayfield is unavailable, with Nick Mullens serving as backup QB.

If Stefanski does not produce two negative tests in time, special teams coordinator Mike Priefer will serve as Cleveland's acting head coach.

There has been no discussion of making a change to the game's status on Saturday, a league source told ESPN's Dianna Russini.

In a statement, the team said that Stefanski, 39, "is feeling fine and will continue his head-coaching duties virtually." Stefanski said Tuesday that he had received the booster on top of being vaccinated.

Browns running backs coach Ryan Cordell also tested positive.

Tuesday, the Browns placed eight players on the COVID-19/reserve list, including four offensive starters in five-time Pro Bowl wide receiver Jarvis Landry, offensive guard Wyatt Teller, tight end Austin Hooper and left tackle Jedrick Wills Jr.

Defensive end Takk McKinley, punt returner JoJo Natson, backup guard Drew Forbes and reserve tight end Ross Travis also were placed on the list.

All eight players are vaccinated, a source told ESPN, meaning they can return to the team after producing two negative tests 24 hours apart.

Stefanski also tested positive for COVID-19 last season going into Cleveland's first playoff appearance in 18 years. He stayed home and watched the game from his basement as the Browns defeated the Pittsburgh Steelers 48-37.