FOXBOROUGH, Mass. -- What has happened to the once-vaunted New England Patriots defense?

The unit that prides itself on transforming on a week-to-week basis to take away an opponent's strength has been shredded on the ground (226 yards allowed to the Indianapolis Colts) and through the air (314 yards, three TDs allowed to the Buffalo Bills) in back-to-back losses that have sparked unexpected concerns.

Things have been markedly different since the Dec. 12 bye, when the team was on a seven-game win streak, which has players wondering how things gone so drastically off track.

"Wish I knew," safety and longtime captain Devin McCourty said in the aftermath of Sunday's 33-21 loss to the Bills, a game in which opposing quarterback Josh Allen was credited for an exemplary performance.

"It's too late in the season to not play your best football and I would say these last two weeks have come down to that; we're playing against teams that are playing the way you're supposed to be playing in late December."

Added linebacker Kyle Van Noy: "We can't point the finger. We've got to get together as a team, come closer, and just got to do the right things."

The Patriots (9-6) are already looking ahead to Sunday's home game (1 p.m. ET, CBS) against the Jacksonville Jaguars (2-13), which has the potential to be a "get-right" matchup against a team playing out the string. But even if that's the way it turns out, there will be a question as to whether New England can deliver that type of performance against playoff-caliber competition.

The season finale at the Miami Dolphins will be the final test before likely postseason competition, when the Patriots are projected to be playing on the road on wild-card weekend.

"Hopefully we can play our best football in January. That's what we need to do. That's what we're planning to do," coach Bill Belichick said in his weekly interview on sports radio WEEI. "There's still a lot in our control. I think before we write the finale to the season, let's see how we finish playing."

One area where Belichick hopes to see improvement is defensively on third and fourth downs. He called that "the story of the game" against the Bills, who were 6-of-12 on third down and 3-of-4 on fourth down, while the Buffalo defense held the Patriots' offense to 1-of-10 on third down.

Belichick noted speedy receiver Isaiah McKenzie had success on "over" routes that take longer to develop because they are farther down the field, which highlights the need for a more disruptive pass rush.

Those were some of the corrections players went over Monday with coaches, as they "flushed it" and looked ahead to Sunday's game against the Jaguars.

"I would say, both [losses], there's not one thing that needs to be fixed. It's overall, everybody playing just a little bit better," McCourty said. "It's not like it's just all bad and we're getting killed, but when we need to make a play, we're not making those plays. It's just not good enough.

"We're starting slow, falling behind, and now we're playing catch-up. You have to play perfect when you play a game like that. It hasn't been good and it's up to us as a team for what's left of the season -- we're guaranteed two games and that's it. That's how we have to approach it, the mentality and mindset we need to have, and if not, the season won't end the way we want."

McCourty added "it's basically playoff games from here on out," and the defense knows what it is capable of based on prior success.

"There's just nothing to talk about. It's that point in the season where you either get it done or you don't," he said.