FOXBOROUGH, Mass. -- Once the New England Patriots were officially eliminated from the 2020 NFL playoffs in Week 15, coach Bill Belichick said there were team-based questions to answer as he now begins looking at things from a big-picture standpoint.

One of the most significant: Why is the roster he assembled with director of player personnel Nick Caserio -- which was embarrassed in a 38-9 loss to the Buffalo Bills on Monday night -- so short on talent?

A combination of shaky drafting, free-agent misses, COVID-19 opt-outs, salary-cap restrictions and the departure of quarterback Tom Brady has contributed to the current snapshot, putting Belichick, 68, on the spot to fix it.

He remains the right person to lead the turnaround, simply because one disappointing season amid a pandemic doesn't erase 20 prior years of unprecedented excellence.

But communicating his vision of how he plans to do so would be a welcome start for the invested, passionate fan base, part of which is still coming to grips with the idea Brady is leading the playoff-bound Tampa Bay Buccaneers.

Change is often hard. And this one cuts deep for many who, while grateful for unprecedented success over two decades, are simply following Belichick's own credo that the past is irrelevant to what happens going forward.

Those inside the walls of Gillette Stadium are expecting a major shake-up in 2021.

"When you have a season like we did this year, and you're not going to the playoffs, you have embarrassing losses, this roster is going to be a lot different," veteran cornerback Jason McCourty said. "There are a lot of guys that are in the locker room that aren't going to be next year."

No question looms larger than the same one that was being asked in March, when Brady officially pulled the plug on his time in New England. Who's the quarterback?

While that will probably warrant the most headlines -- as it did throughout 2020 because of Cam Newton's uneven play and Jarrett Stidham never emerging as the possible heir as some projected -- it would be wildly missing what is an even greater issue.

It's true that a team without a quarterback has little chance, but given the talent drain the Patriots have experienced at tight end and receiver, it's debatable that any quarterback would have had a chance to succeed in New England in 2020.

One of the eye-opening parts of the challenging season was the Arizona Cardinals consistently playing a goal-line defense in the middle of the field against base offensive personnel in Week 12, a sign that they had little regard for the Patriots' tight ends and receivers.

So the team-building approach was badly flawed in that area, which was probably part of the reason Brady headed to the exit in the first place.

Upgrades are needed across the roster. Tight end. Receiver. Quarterback. Defensive tackle. Outside linebacker.

It's arguably as challenging a rebuild as Belichick has had in his 46 NFL seasons, right there with his initial days with the Cleveland Browns in 1991 and his arrival in New England in 2000.

If there is a silver lining, it's that the salary-cap picture is promising, giving the Patriots room to maneuver while balancing the possibility of re-signing their own key free agents (e.g. center David Andrews, guard Joe Thuney, defensive tackle Lawrence Guy, cornerback J.C. Jackson, etc.) and eyeing others around the league. They also should enter the 2021 NFL draft with 10 picks, six of which are within the first four rounds, once compensatory selections are awarded.

But first, the Patriots conclude the regular season with a home finale against the New York Jets on Sunday (1 p.m. ET, CBS) before officially moving into 2021.

For those wondering about Belichick's motivation to take on such a challenge, his competitive spirit was evident when he wrapped up his weekly radio interview Tuesday by saying: "Look forward to this final game with the Jets and the coming year, and hopefully returning to a higher level of coaching and playing performance for the Patriots."

Safeties coach Brian Belichick, who has a deep history around the organization, said Tuesday that no matter the record over the years, a common thread has been a team-wide relentless work ethic. He sees the same thing now, particularly with the head coach set to oversee such a critical offseason.

"No one works harder than my dad," he said. "He sets the tone for the entire organization."