With kickoff nearly a month away, the NFL considers the use of virtual fans in stadiums a viable option for game days, a league source said Thursday.

The NFL utilized the practice during the virtual draft in April and has a similar template available in the absence of real fans. The NBA has found success with a similar model for its game action in its bubble on the Walt Disney World Resort campus in Florida.

The league must get creative because of the challenges of the coronavirus pandemic. The Las Vegas Raiders have announced that no fans will attend home games for the inaugural season in Allegiant Stadium, and fans will not be permitted in several other stadiums across the league under current conditions.

Some teams still are hoping for 33% to 40% capacity in their stadiums to start the season, but that's hardly a slam dunk given the national spike in positive tests.

Either way, the NFL is prepared to enhance the game-day experience with potentially sizable virtual backdrops inside stadiums, the source said.

Enhanced virtual advertising also is an option to fill vacant seats.

The NFL and players union have reached a "side letter agreement" on revenue share, opt-out clauses and other issues amid the pandemic. But the sides continue to discuss game-day protocol, including the handling of potential outbreaks before games. A source said no algorithm currently exists for how many positive tests would force the cancellation of an NFL game.

The NFLPA on Thursday announced that 56 players have tested positive for COVID-19 since training camp reporting began. Teams hope those numbers dwindle with players inside their controlled atmospheres.