The Washington Football Team was optimistic it might get one of its star defensive ends back for a critical stretch to close the season. Instead, the team learned it will have to wait a bit longer.

Montez Sweat, who was on injured reserve because of a fractured jaw, was placed on the reserve/covid-19 list on Wednesday, the team announced. The team did not say whether he tested positive or was deemed a close contact to someone who did.

According to a person with knowledge of the situation, Sweat is unvaccinated, which means he will miss at least five days (if a close contact) but possibly 10 or more (if he tested positive).

“I can’t tell you,” Coach Ron Rivera said when asked about Sweat’s quarantine. “Just hearing the news this morning and knowing we had to put him on the protocol list. We’ll go from there. Hopefully we’ll get some good news very shortly with that. So it’s a not a long one, hopefully.”

At a minimum, Sweat is ruled out for Sunday’s game against the Dallas Cowboys. If he tested positive, his minimum 10-day quarantine would end the day before Washington’s Week 15 game against the Philadelphia Eagles. But NFL protocols require symptomatic individuals to complete a ramp-up period before returning fully to practice or games, and Sweat will have missed more than a month of practice by that point because of his time on injured reserve.

Sweat said in June that he “probably won’t get vaccinated” and that “I don’t see me treating covid until I actually get covid.” At the start of training camp in late July, Washington had one of the league’s lowest player vaccination rates, prompting Rivera, who is immunocompromised from cancer treatments, to speak out publicly about players’ reluctance to get vaccinated.

“It’s frustrating, especially in the fact that last year we were the number one team against covid,” he said at the time. " … Now, for whatever reason, we have some reluctance … to get the vaccine. These young men have to make the decisions for themselves, but hopefully they can understand just how impactful not getting the vaccine is. You’d like to believe all the news that’s been out there, that the people that are being hospitalized and are dying from covid right now are those that aren’t vaccinated.”

To provide players with more information about the vaccines, the team had Kizzmekia S. Corbett, an immunologist and leading vaccine researcher, speak to players and coaches via video conference in June.

The team’s vaccination rate steadily increased, but it had seven players land on the covid-19 list during training camp. Sweat is only the second Washington player to go on the list during the season, along with second-year offensive lineman Saahdiq Charles.

“This time of year, with the potential for the breakthroughs and all that, it’s just a frustrating period; it really is,” Rivera said Wednesday. “It’s just the unfortunate part. But we’re okay. We’re going to be fine. We like our guys, and we’re looking forward to Sunday.”

The news comes just as Sweat appeared close to returning from injury. The third-year defensive end suffered a fractured jaw late in Washington’s loss to the Denver Broncos and was placed on injured reserve Nov. 13. Pending final clearance from doctors, Sweat was on track to practice this week, Rivera said.

Instead, his extended absence — coupled with Chase Young’s season-ending ACL injury — means more time for second-year defensive ends Casey Toohill and James Smith-Williams. The two have played alongside veteran tackles Jonathan Allen and Daron Payne the past four games and have been among the many reserves who have helped Washington to a four-game winning streak that has propelled it to the sixth spot in the NFC.

“I think Casey Toohill and James Smith-Williams and Danny Wise and Bunmi [Rotimi] and Shaka Toney — they’re not going to get the credit they deserve, but I mean, damn,” Allen said after Washington’s win at Las Vegas. “ … They’re making great plays for us — plays that might not show up in the stat book but big plays.”