The Washington Football Team added three more players to its covid-19 reserve list Thursday, further thinning its roster ahead of Sunday's pivotal matchup with the Eagles in Philadelphia. Safety Kam Curl and centers Tyler Larsen and Keith Ismael were added to the list, bringing the team's total to 21. It remains unclear whether any of those players will be able to return in time for Sunday's game, although a change the NFL made Thursday to its coronavirus protocols could allow vaccinated players who are asymptomatic to come back sooner. Washington's active roster has been whittled to 40 players by the outbreak, leaving it in a precarious position just days before it travels to Philadelphia for a matchup with major playoff implications. Washington (6-7) is in seventh place in the NFC, which would be good enough for the final wild-card spot at season's end, but a loss to the Eagles (6-7) would deliver a significant blow to its postseason chances. "Obviously it's a challenging situation," offensive coordinator Scott Turner said. "This game is coming Sunday — no excuses in the NFL. We just got to get our guys ready to play." The NFL adjusted its protocols Thursday after more than 100 players tested positive over the past week. Through at least the rest of Week 15, all teams are in enhanced protocols and have to hold meetings ­virtually, with players and coaches required to wear masks indoors regardless of vaccination status. Should healthy, vaccinated pro athletes who test positive play on? Not yet, experts say. But players and staffers who are fully vaccinated and asymptomatic could return a day earlier than they would have under the previous protocols, which required two negative tests separated by 24 hours. Now those on the covid-19 list can return after two negative tests taken on the same day — or if they meet a certain cycle threshold value, an indirect indicator of how much virus a person is carrying. But there are caveats to the change. For game-day testing, the only way a player could become eligible to play is with two negative rapid-result tests. For players who are unvaccinated, the usual protocols remain in place: They must isolate for 10 days before they can return to the team after a negative test. Allen Sills, the NFL's chief medical officer, said during a conference call with reporters Thursday that the uptick in positive tests can be attributed to the omicron variant, an increase in respiratory illnesses as the weather turns colder and a decrease in immunity.