The NFL toughened its coronavirus protocols Wednesday, as it attempts to complete its season amid deteriorating conditions nationally.

The announcement came as the Las Vegas Raiders continued to experience coronavirus-related issues, with a significant number of defensive players being placed on five-day quarantines that will keep them off the practice field this week in advance of Sunday’s game against the Kansas City Chiefs.

The league informed teams in a memo from Commissioner Roger Goodell that, beginning Saturday, it is implementing additional measures by making its intensive protocols applicable to all teams at all times. Those enhanced measures are designed to halt spread of the virus within teams’ facilities and have applied, to this point, only to those teams with positive coronavirus cases and those known to have been exposed to the virus.

The NFL said that teams operating under the enhanced protocols, which include additional mask-wearing requirements and provisions for team meetings to be held remotely, had reduced close contacts to individuals with the coronavirus by more than 50 percent.

“These sustained reductions and the resulting health and safety benefits make it appropriate to implement the Intensive Protocols on a mandatory, leaguewide basis,” Goodell wrote in Wednesday’s memo, a copy of which was obtained by The Washington Post.

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The NFL cited the spike in cases around the country and the added risks presented by holiday gatherings.

“Today, we are implementing further enhancements to our protocols to address current conditions, in particular the sharp growth in covid-19 cases in our communities and the related increase in cases among our players and other club employees,” Goodell wrote. “The upcoming holidays, beginning with Thanksgiving next week, will introduce new risks of exposure that we need to address now.”

NFL cases have been on the rise in recent weeks. The league and the NFL Players Association announced Tuesday there were 17 new confirmed positive tests among players and 35 new confirmed positives among other personnel in testing results from Nov. 8 to Nov. 14. NFL leaders have said their data shows that the virus mostly is not being spread within team facilities and the sport’s cases result mostly from players, coaches and team staffers being exposed outside those facilities.

The intensive protocols require mask-wearing by players, coaches and staffers at all times at team facilities, even on the practice field (players can opt instead for face shields on their helmets). Team meetings must be held virtually, with a few exceptions. Meals for players must be served grab-and-go. The amount of time spent in locker rooms is limited, and the number of individuals permitted in weight rooms is restricted.

The NFL said 28 of the 32 teams already have operated at some point under the intensive protocols; 16 teams have been subjected multiple times to the enhanced measures.

Goodell wrote that “it will likely be necessary to take further steps to address broader conditions” as the season progresses. The NFL has had five straight weeks with minimal disruption to its schedule after two weeks with rampant rescheduling of games, aided by a protocol tweak requiring five-day quarantines for those classified as high-risk close contacts to an individual who tests positive.

“It has been said many times that our 2020 season cannot be ‘normal’ because nothing about this year is normal,” Goodell wrote Wednesday. “Flexibility and adaptability have been critical to our success to date and we must continue with that approach. I am convinced that if we remain focused and committed to adhering to our protocols, and to adjusting them as experience requires, we can play a full 2020 season that is not simply normal, but extraordinary.”

The Raiders placed seven players — defensive backs Johnathan Abram and Isaiah Johnson and defensive linemen Maliek Collins, Johnathan Hankins, Arden Key, Kendal Vickers and David Irving — on their covid-19 reserve list Wednesday. Irving is on the team’s practice squad. The Raiders had placed defensive Clelin Ferrell and cornerback Lamarcus Joyner on the list Tuesday.

Ferrell reportedly tested positive for the coronavirus. The other players were placed on five-day quarantines, according to a person familiar with the situation, after being classified as high-risk close contacts. Most or all of the players placed in quarantine as close contacts are expected to be eligible to play Sunday night in Las Vegas against the Chiefs unless they test positive, according to that person.

Earlier this month, the NFL fined the Raiders $500,000 and stripped them of a sixth-round draft choice for protocol violations. Coach Jon Gruden, the team and some Raiders players had been fined for previous violations.

The Denver Broncos announced Wednesday that defensive coordinator Ed Donatell is home recovering after being taken to a hospital last week with coronavirus-related symptoms. Donatell is doing light physical activity and has begun to participate in remote team meetings, according to a team spokesman.