Patrick Mahomes is unreal. The Kansas City Chiefs' offense that he leads is next to unstoppable. But Kansas City’s dreadful defense might keep the Chiefs from reaching the Super Bowl this season, as the New England Patriots demonstrated Sunday night in Foxborough, Mass.

The first 43-40 game in NFL history went in the Patriots’ favor, as they prevailed on a 28-yard field goal by kicker Stephen Gostkowski as time expired. The greatest quarterback the sport has ever seen, Tom Brady, beat the greatest quarterback of the league’s pass-happy 2018 season, Mahomes.

No one, except for those who crave the sort of rugged defense that so rarely is seen in the NFL these days, would mind seeing a rematch in January in the AFC championship game.

“There wasn’t a lot of margin of error,” Brady said during a postgame interview with NBC. “They made some big plays. But we made our fair share, too. I don’t know if we punted tonight. I still think we can play better than that. It was a great win. Great win. I’m really happy we won.”

No, the Patriots didn’t punt. The Chiefs punted once. The Patriot amassed 500 yards of total offense, to 446 for the Chiefs. Brady threw for 340 yards and a touchdown. Mahomes threw for 352 yards and four touchdowns. The Patriots had the football last. That was enough to win.

The Chiefs had a chance to improve to 6-0 and lap the rest of the AFC field. Instead they dropped to 5-1. And there are plenty of reasons to be concerned about their defense. The Chiefs were ranked last in the league in total defense entering this week’s play. They were 31st against the pass and 23rd against the run.

Things didn’t improve Sunday night. The Patriots piled up 173 rushing yards, including 106 by rookie tailback Sony Michel. The deficiencies of the Kansas City defense kept the Chiefs from winning on a night when they had two 100-yard receivers, wideout Tyreek Hill and tailback Kareem Hunt, and an 80-yard rusher, Hunt. They lost on an evening when Mahomes threw second-half touchdown passes of 67 yards to Hunt and 75 yards to Hill.

“He made some great throws,” Brady said of Mahomes. “Big play after big play. He’s a great player. They’ve got a lot of good skill guys and they’ve got a good offense; 43-40, we won. I don’t care if it’s 3-0 or 43-40. Good win.”

The Patriots seemed to have some answers on defense for Mahomes and the Chiefs. They led 24-9 at the half, limiting the Chiefs to field goals.

The Patriots seemed focused on keeping Mahomes in the pocket and on jamming tight end Travis Kelce at the line of scrimmage. They gave Mahomes different looks. Mahomes was a bit off target with his first-half passing. He threw a pair of interceptions, one to linebacker Dont’a Hightower when Hightower dropped into coverage, and one just before halftime in which he was pressured by Hightower and forced a pass into heavy traffic in the end zone.

“It looks like it’s too big for him tonight,” Tony Dungy, who faced the Patriots in so many big games as coach of the Indianapolis Colts, said of Mahomes at halftime on NBC.

The stage certainly wasn’t too big in the second half for Mahomes, as the second-year pro reinforced that he is the likely MVP of this season and the sport’s next quarterbacking megastar. The Chiefs rolled to 31 second-half points on the road against a Bill Belichick-coached defense. Mahomes threw four second-half touchdown passes.

Brady lost a fumble during a stretch in which the Patriots seemed to be coming unglued. Chiefs Coach Andy Reid sparked a debate by having his team kick an extra point, rather than attempting a tying two-point conversion, in the final moments of the third quarter. It was a game with a bit of everything — except defense.

Yes, the Chiefs are playing without defensive standouts like safety Eric Berry, sidelined by Achilles’ tendon and heel injuries, and outside linebacker Justin Houston, who was on the inactive list Sunday night because of a hamstring injury. Their returns — provided that Berry indeed plays this season, as the Chiefs seem to expect — should help.

But this is the NFL. Injuries are part of the deal. Excellent teams find ways to cope and adjust. This is a Chiefs defense that hasn’t done anything particularly well this season. Opposing offenses have been able to run the ball. They have been able to pass the ball. It is a season of wide-open offensive football across the league. But the Chiefs are taking it to the extreme, on both offense and defense.

The Patriots couldn’t stop the Chiefs, either, on Sunday night. But the Patriots get the benefit of the doubt that Belichick and his assistants will find a way to work something out by the playoffs. A Reid-coached team doesn’t get the same benefit of the postseason doubt.

Brady scored on a four-yard scramble in the fourth quarter, his first touchdown run of more than one yard since 2012. Brady broke a tackle by Chiefs rookie Breeland Speaks, who told reporters after the game that he thought Brady already had released a pass.

“It took a long time for me to get those four yards,” Brady said.

The Chiefs had a touchdown set up by a 97-yard kickoff return by rookie Tremon Smith. Brady began to find his old standby, tight end Rob Gronkowski, late in the game. It was a 39-yard Brady-to-Gronkowski connection that set up Gostkowski’s winning kick. Afterward, Brady ran across the field to greet Mahomes.

That’s a meeting that everyone should hope to see again this season.