After starting right tackle Trent Brown was placed on the reserve/COVID-19 list on Wednesday, left tackle Kolton Miller, left guard Denzelle Good, center Rodney Hudson and right guard Gabe Jackson each landed there Thursday.
All four were all deemed "high-risk contact" after Brown tested positive for COVID-19. They each were last in contact with Brown on Monday and will need to quarantine for five days since their last contact, providing a path to playing Sunday if they test negative.
As ESPN's Paul Gutierrez noted, the Raiders now have only five active offensive linemen on the 53-man roster and two on the practice squad, coming short of the eight minimum on a game day.
Las Vegas was scheduled to face the Tampa Bay Buccaneers on Sunday night, but kickoff has been moved to 4:05 p.m. ET, per ESPN's Adam Schefter. The Arizona Cardinals and Seattle Seahawks will take the spot in prime time.
"These decisions were made out of an abundance of caution to ensure that a game would be available for fans on Sunday Night Football," the league said in a statement.
"We expect the Buccaneers-Raiders game to be played on Sunday afternoon. Scheduling decisions are made to ensure the health and safety of players, coaches and game day personnel and in consultation with medical experts."
The NFL and NFLPA have also been investigating the Raiders as to whether they have followed protocols, according to Tom Pelissero of NFL Network. The league believes players were spending time together without masks and that Brown wasn't always wearing his league-mandated tracking device.
Several Raiders players were previously fined for attending a September fundraiser where some players did not always wear a face covering inside a crowded indoor room.
The league has been forced this season to move two games to different weeks as a result of COVID-19 outbreaks involving the Tennessee Titans and New England Patriots. There have also been games delayed to Monday or Tuesday to help ensure players no longer tested positive.
With the Raiders dealing with significant uncertainty and limited practice time during the week, playing Sunday could be a difficult task.