According to ESPN's Adam Schefter and Kimberley Martin, Cleveland Browns quarterback Case Keenum has tested positive for COVID-19, potentially leaving the team without its top two quarterbacks for Saturday's game against the Las Vegas Raiders.

Baker Mayfield, the team's starting quarterback, tested positive for the virus earlier this week and is now on the reserve/COVID-19 list.

Nick Mullens, who was upgraded to the active roster on Thursday, is now expected to start for the Browns at quarterback. Mullens started 16 games for the 49ers between 2018 and 2019 but has yet to throw a pass for the Browns.

On Thursday, Cleveland quarterback Case Keenum practised.

The NFL eased the testing standards for cleared vaccinated people on Thursday, perhaps allowing players on the list to return sooner. The NFL has stated that it has not considered relocating the Browns-Raiders game to another day.

Mayfield criticized the league on Thursday, tweeting: "@NFL Make up your damn mind on protocols. Showing up and making only 3 teams test?!? All so you can keep the game as scheduled to make money."

"Actually caring about player safety would mean delaying the game with this continuing at the rate it is .... But to say you won't test vaccinated players if they don't have symptoms, then to pull this randomly. Doesn't make any sense to me," he added in another tweet.

Browns standout defensive end Myles Garrett, like Mayfield, has questioned the league's testing practises.

Garrett said it was odd that players weren't tested before entering the team's facility on Thursday, implying that those who were positive may have entered the building, potentially spreading the virus.

"It almost seemed like we were just ignoring it instead of addressing the issue,'' he said. "We should go ahead and test and then allow in the building but not before you get results, and that is how it should be.

"The lack of testing that we have done all year I kind of feel like has led to this point. Only testing one time a week and guys doing their own thing on Monday and Tuesday with their time off, it was kind of a recipe for disaster.''

According to Schefter and Martin, four more Browns defenders have tested positive, including safety Grant Delpit and cornerback A.J. Green, increasing the total number of players in the protocols to around 20. On Thursday, the Browns added safety Ronnie Harrison Jr. on the COVID-19 list.

The Browns might be without their top three safeties and three of their top five cornerbacks if the players on the virus list aren't ready to return by Saturday. Safety John Johnson was placed on the COVID-19 list earlier this week, while cornerback Greg Newsome was ruled out due to a concussion.

The Browns activated tight end David Njoku from the COVID-19 list on Thursday. Njoku returned to the squad in time for practise on Thursday after missing last week's game against the Baltimore Ravens.

Coach Kevin Stefanski missed practise on Thursday after testing positive earlier in the week. Special teams coordinator Mike Priefer will serve as Cleveland's acting head coach if Stefanski is unable to return for Saturday's game.

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