USA Today

Players began reporting to team facilities last Thursday, and they must record three negative COVID-19 tests before they are allowed to begin physicals and get their hands on team equipment. On Tuesday, the NFLPA announced that there have been 21 positive tests in the testing conducted as part of the training camp reporting process, according to Pro Football Talk. Rookies, injured players and quarterbacks were allowed to start reporting last week while veterans from most teams began reporting to camp on Tuesday.

It's important to note, however, that the union did not announce the total number of tests that were completed overall. Players who test positive for COVID-19 will be placed on a reserve list until they are no longer experiencing symptoms and/or receive multiple negative tests. The new reserve list category was created for a player who either tests positive for COVID-19 or who has been quarantined after having been in close contact with an infected person or persons. If a player falls into either of these categories, his club is required to immediately place the player on the reserve/COVID-19 list. Clubs may not disclose whether a player is in quarantine or is positive for COVID-19.

We do know of several rookies who have been placed on the reserve/COVID-19 list. The Jacksonville Jaguars placed four rookies on reserve and a few other notable players such like Isaiah Wilson of the Tennessee Titans, Justin Jefferson of the Minnesota Vikings and Ke'Shawn Vaughn of the Tampa Bay Buccaneers were placed on the COVID-19 list as well. Overall, the league announced that a total of 107 players have tested positive over the course of the offseason. 

As the week progresses, more players will announce that they will be opting out of the 2020 NFL season due to the pandemic. To keep up with who will pass on playing this year, check out CBS Sports' opt-out tracker here