After a 2020 season that saw COVID-19 hotspots develop in multiple organizations, the NFL hoped experience, knowledge and a high vaccination rate would head off another spate of intense roster infections in 2021.

That hope hit an iceberg this week.

After setting a single-day record for COVID positives across the league Monday, the Los Angeles Rams were forced to close their team facility on Tuesday, while the Cleveland Browns also moved into the league’s enhanced protocols after placing eight players — including four starters — onto the COVID reserve list. The NFL hit a single-day high of 37 positive tests among players Monday, then rolled into Tuesday with the Rams and Browns both bracing for more positive tests.

As of Tuesday, the league’s COVID reserve list had ballooned to nearly 100 players, with the expectation that number will climb over the course of the week.

For the Browns in particular, further tests could stress the team’s ability to field a competitive team on Saturday against the Las Vegas Raiders, a game that was flexed to Saturday by the NFL several weeks ago as part of an effort to showcase matchups after the end of college football’s regular season. Now it’s going to highlight the league’s renewed difficulty in stopping hotspots for coronavirus spread inside franchises.

With the Browns already placing a sizable chunk of their active game roster on the list, it could also challenge the resolve of the league office if the spread of infection continues to spiral. NFL commissioner Roger Goodell laid down a zero-tolerance policy in the offseason when it came to outbreaks inside teams, stating that games would not be moved out of television slots in 2021 and that teams will incur potential fines and game forfeiture if they are unable to play due to the spread of COVID. No team had to forfeit in 2020, though several games were pushed back, sometimes even into midweek.

Among some of the notable names that landed on the COVID-reserve list in the past several days: wideout Odell Beckham Jr., cornerback Jalen Ramsey, tight end Tyler Higbee and offensive tackle Rob Havenstein of the Rams; defensive end Takk McKinley, tight end Austin Hooper, wideout Jarvis Landry, guard Wyatt Teller and offensive tackle Jedrick Wills of the Browns; Los Angeles Chargers offensive tackle Rashawn Slater; Dallas Cowboys wideout Cedrick Wilson; Houston Texans linebacker Kamu Grugier-Hill; Kansas City Chiefs wideout Josh Gordon; Miami Dolphins running backs Myles Gaskin and Phillip Lindsay; Minnesota Vikings running back Alexander Mattison; New York Giants wideout Kadarius Toney; Philadelphia Eagles wideout Quez Watkins; Washington Football Team defensive tackle Jonathan Allen; and Carolina Panthers running back Christian McCaffrey.