Williams was placed on the list after coming in close contact with someone who has COVID-19, a source confirmed to ESPN. He did not test positive, the source said. Per NFL/NFLPA protocol, Williams must isolate for five days after the initial exposure.
The Ravens, who made the trip to Philadelphia on Saturday afternoon, are now expected to be without two starting defensive linemen for Sunday's game against the Eagles. Defensive end Derek Wolfe (neck/concussion) is listed as doubtful.
Williams has been a key figure in the Ravens' run defense. With him in the lineup since 2017 (47 games), Baltimore has held teams to 87.2 yards rushing per game and 3.9 yards per carry. In six games without Williams over that span, the Ravens have given up 160.3 yards rushing per game and 4.6 yards per carry.
Williams did not practice Thursday and Friday for non-injury related reasons. After Friday's practice, coach John Harbaugh said Williams had "a personal excused absence."
On Thursday and Friday, Ravens players were spotted wearing masks while walking out to the practice field, which is not something they previously did.
When asked a little over two weeks ago about what it will take to avoid COVID-19, Williams said: "Do as much as you possibly can to protect you and the family and the people that you love. Sometimes if you catch it, you catch it. Sometimes, it just is what it is and it's inevitable."
Williams becomes only the second Ravens player to be put on the reserve/COVID-19 list and the first since training camp officially started.
The Ravens' defense currently leads the NFL in fewest points allowed, giving up 15.2 points per game.