The Chiefs had no need to mess with their offense — not when they had a 23-year-old MVP in Patrick Mahomes, an elite playcaller in Andy Reid, and the fastest arsenal in the NFL with Tyreek Hill, Sammy Watkins, Travis Kelce and newcomer Mecole Hardman.

But the Chiefs’ defense is markedly different from the one that gave up 80 points in two losses to the Patriots last season. Defensive coordinator Bob Sutton was let go, and Reid hired an old friend and old Patriots nemesis to turn around the defense – Steve Spagnuolo, who you may remember as the Giants’ defensive coordinator who crushed the Patriots’ dreams in Super Bowl 42.

The Chiefs switched their scheme from a 3-4 under Sutton to a 4-3 under Spagnuolo, and discarded several players who no longer fit — most notably pass rushers Dee Ford and Justin Houston, while also moving on from safety Eric Berry. The pass rush is now anchored by Frank Clark, formerly of Seattle, and Emmanuel Ogbah, formerly of Cleveland. And they replaced Berry with Tyrann Mathieu, formerly of Arizona and Houston.

Bill Belichick said Wednesday he knows exactly what to expect from Spagnuolo, the Grafton native who has coached in the NFL since 1999, including 10 seasons as a coordinator or head coach.

“It’s Steve’s scheme — a lot of pressure, blitz-zone,” Belichick said. “They play more zone, but they can play man. So, he’ll mix it up, but they keep the pressure on, and they turn the ball over.”

The Chiefs are just 16th in points allowed (22.1 per game) and 25th in total defense, but may be finally getting into their groove following so much offseason upheaval. They have created seven turnovers the past two games, a 24-17 win over the Chargers and a 40-9 win over the Raiders last Sunday.

“We’re better than we were when we first started, but heck, we have plenty of room to improve here,” Reid said this week. “This will be a nice challenge for us.”

The Chiefs have the most room to improve in their run defense, which has been atrocious all season. They rank 30th in yards per game (141.3) and tied for 30th in yards per carry allowed (5.1). They have created a negative play on just 5.5 percent of rushing attempts, which ranks 29th. And the Chiefs have caused a three-and-out just 15 percent of the time, which ranks 31st.

Even in last week’s blowout win, the Chiefs struggled against the run. Raiders running back Josh Jacobs rushed 17 times for 104 yards (6.1 average), opening with runs of 12, 8, 8, 15, and 7 yards, and ripping off an impressive 35-yarder on a sweep to the left. And three weeks ago, Chargers running backs Melvin Gordon and Austin Ekeler combined to rush 19 times for 93 yards (4.9 average), including runs of 21 and 18 yards. If ever there were a game for Sony Michel and the Patriots’ run game to get back on track, it’s Sunday.

But the Chiefs’ pass defense is slowly improving, sitting at about league average or better in several statistics. The Chiefs are 16th against the pass (231 yards per game), 11th in yards per attempt (7.13), 11th in sacks (34), and 19th on third down (36.9 percent).

Their opponents’ passer rating is 86.1, eighth-best in the NFL. They do even better on the deep ball, allowing a passer rating of 58.2 on passes of at least 21 yards in the air, which is sixth-best. They have only allowed one touchdown on a deep ball all season. And the Chiefs have done well in the red zone, allowing a score on 83 percent of possessions, the ninth-best mark in the NFL.

The Chiefs play a four-man front, and they have some big-time playmakers. The most dangerous is the man right up the middle, Chris Jones, a second-team All-Pro in 2018 who leads the team with six sacks this season. The Patriots blanked him on the stat sheet in the AFC Championship game, but he’ll be a load for Joe Thuney, Shaq Mason and third-string center James Ferentz.

Clark, though he only has five sacks, is still an excellent pass rusher from both sides, and his speed could give Isaiah Wynn and Marcus Cannon a lot of trouble.

Spagnuolo isn’t a high-volume blitzer — again, the Chiefs blitz about the league average (about 10 times per game) — but he certainly likes to get creative with zone blitzes. The Chiefs often will bring six or seven players to the line of scrimmage, forcing the quarterback and offensive line to figure out quickly which players are rushing and which are dropping into coverage. Last week against the Raiders, Spagnuolo created a free rush for free safety Juan Thornhill, forcing Derek Carr to throw the ball away. The Chiefs allow a passer rating of 81.8 against the blitz, which is the eighth-lowest in the NFL.

As Belichick mentioned, the Chiefs like to play a lot of zone coverage. They primarily show a two-deep safety look, but will do plenty of post-snap rotating into other zone coverages. Mathieu, a ballhawking defensive back who can play cornerback, strong safety or free safety, did a great job of baiting Carr into an interception last week by disguising his zone coverage and being in perfect position to undercut the throw. Mathieu is interchangeable with the other safety, Thornhill, a rookie who secured his first career pick-six last week by jumping a slant route over the middle.

But the Chiefs certainly have the talent to play man coverage, and had several plays against the Raiders, where Carr danced in the pocket forever and couldn’t find anyone open.

The one area in which the Chiefs’ pass defense appears to struggle is in yards after the catch, where they allow 6.2 per catch, the third-most in the NFL. And the guys the Patriots may want to target are Morris Claiborne and Daniel Sorenson, who have played more recently with Kendall Fuller slow to return from a thumb injury.

This is not the ’85 Bears coming to Foxborough Sunday. The Patriots should have success running the ball, and Tom Brady should look better than he did last Sunday in Houston.

But the Chiefs don’t need a dominant defense to win. With Mahomes and that track team of an offense, the Chiefs’ defense just needs to be good enough. And after 12 weeks of playing together, the Chiefs’ defense may have what it takes to come into Foxborough and pull off the win.