FOXBOROUGH, Mass. — After nearly four months of games, one thing seems certain about the New England Patriots.

There’s a lot of uncertainty.

Sure, Tom Brady and Rob Gronkowski probably will make big plays and the defense likely will give some up. And, somehow, Coach Bill Belichick and his staff will make critical adjustments when problems occur.

But just how good are the Patriots as they start their bye week with a 13-3 record, wins in their last eight games and the AFC’s top seed? Can they make the desired progress once they return from Monday’s day off? Are they good enough to win their opening playoff game for the first time in three years?

Maybe, but Belichick knows there’s plenty of work left to do.

“Obviously, it’s a good feeling to have a 13-3 regular season,” he said Monday. “(There were a) lot of ups and downs along the way, a lot of challenges that we had to face. … Now it’s really time to end that chapter and (go) onto the next one. There’s certainly a lot of things that we can do better and improve on.”

Begin with the slow starts.

On Sunday, the Bills led 21-0 after the first quarter before the Patriots won 49-21. In their previous game, the deficit was 17-0 at halftime, but the Patriots came back for a 27-24 victory over the Dolphins. And in the game before that, they gave up 167 yards rushing in the first quarter alone to the Denver Broncos and trailed 17-6, a deficit the Patriots erased with a 41-23 win.

But they have no illusions that a similar start can be overcome even though they have home-field advantage throughout the playoffs where they will play Denver, Pittsburgh or Cincinnati on Jan. 14.

“We just start slow,” tight end Aaron Hernandez said. “It has been like that all season, but it has to change now.”

During the regular season, the Patriots played only two games against teams that finished with winning records and lost both — 25-17 to the Steelers and 24-20 to the New York Giants. Those teams, plus the Broncos, are their only regular-season opponents who made the playoffs.

But the Patriots’ three losses were by a combined 15 points and two were decided in the final minute.

“We’ve got to start strong,” Gronkowski said. “We were lucky enough to even come back against Buffalo, losing by that much, 21. We’ve got to start fast, for sure, and we’ve got to play all four quarters.”

The defense hasn’t done that very much. On Sunday, Belichick was still tinkering with his secondary, putting starting cornerback Devin McCourty at safety and giving wide receiver Julian Edelman considerable time in the defensive backfield. The result? Four interceptions.

The Patriots allowed 402 yards against the Bills, dropping their average to 411.1. For the season, they gave up the second most yards to the Green Bay Packers, who finished at 15-1. The Patriots had given up the highest average from their third game through the 15th.

“We are going to use this week to make sure that we get better,” McCourty said. “I think we are a very confident football team.”

Despite all those yards, the Patriots have been decent at keeping teams from scoring. They’re 15th in the 32-team NFL with 21.4 points allowed. But four of the other five AFC playoff teams have given up fewer.

So it shouldn’t be as easy for Brady to keep putting up big numbers — or leading his team from behind. The Patriots led the AFC with 32.1 points per game with the NFL’s most productive trio of receivers that allowed him to throw for 5,235 yards, second most in league history.

Wes Welker led the NFL with 122 catches, Gronkowski scored 18 touchdowns and set a single-season record for tight ends with 1,327 yards receiving. Hernandez, a tight end with the elusiveness of a wide receiver, had 79 receptions for 910 yards and seven touchdowns.

With all those options, Brady doesn’t decide where to throw until the defense shows its coverage plan.

“Whatever coverage they run dictates where I start my read,” he said. “If that first guy is open, he gets the ball. We never predetermine who we’re going to throw to. You just drop back and you try to find the open guy.”

That shouldn’t be as easy in the AFC playoffs where four of the nine stingiest pass defenses in the league reside. Pittsburgh is ranked first in fewest yards passing allowed, Houston third, Baltimore fourth, Cincinnati ninth and Denver 18th.

For now, Belichick is getting ready for the three he could face in the next game.

“You know what the possibilities are and who (the next opponent) could be so you get a little bit of a jump start on those teams, as far as breaking down film and looking at them. Two of the three we’ve played,” he said. “A lot of it is working on what we need to work on, working on things that have been a problem for us.”