Nearly the entire Las Vegas Raiders' starting defense has been placed on the team's reserve/COVID-19 list ... after DE Clelin Ferrell tested positive for the virus on Wednesday.

At least 7 players -- including Lamarcus Joyner, Johnathan Abram, Maliek Collins, Johnathan Hankins, Isaiah Johnson, Arden Key and Kendal Vickers -- were placed on the list after being determined as close contacts to Ferrell this week.

But, it's not a lost cause for the Raiders just yet -- the players WILL be eligible to suit up Sunday night against the Kansas City Chiefs if they continue to test negative.

However, the batch of players will not likely be cleared to rejoin the team until Saturday at the earliest ... which will be tough as the Silver and Black prepare for Patrick Mahomes and Co.

Of course, the Raiders have had their fair share of fines from the league due to COVID-19 violations ... including head coach Jon Gruden, who has been hit with $100k and $150k penalties this season.

The rise in positive COVID-19 cases across the league forced the NFL to issue a memo to all 32 teams, requiring them to go into intensive protocols for the remainder of the season.

Under the required protocols -- which begin on Saturday -- all team meetings will be held virtually or in large spaces and masks or face shields must be worn at all times at the team facility.