The NFL is preparing a COVID-19 contingency plan in which it temporarily promotes an official to work as a referee during the full slate of games Sunday, according to an NFL source.

The move is yet another twist in the league's effort to play amid the COVID-19 pandemic.

A number of referees and other crew members have been sidelined this season by COVID-19 protocols, but the league has been able to cover for them with other contingency plans. In Week 15, for example, it assigned referee John Hussey to handle two games -- one on Thursday night and one on Monday night -- to cover for referee Clay Martin. In Week 16, referee Adrian Hill worked games on Friday and Sunday after referee Shawn Smith was removed from the schedule.

The NFL has not publicized testing results for officials this season, but as has been the case for players and coaches, some have missed games because of close contacts rather than positive tests. Regardless, doubling up referees in Week 17 would not be possible because all 16 games are scheduled for Sunday.

The league has a total of 17 referees and crews, one more than it needs to cover a full schedule. But according to the NFL source, if multiple referees are unavailable, the league will tap into its referee training program and elevate another crew member -- an umpire, down judge, line judge, field judge, side judge or back judge -- to serve as a referee. If that happens on short notice, that crew will work the game with six members instead of the usual seven, much as it does when an official is injured during a game.

ESPN NFL Insider Adam Schefter contributed to this report.