KANSAS CITY, Mo. >> The Lions walked into roaring Arrowhead Stadium tonight, where the Kansas City Chiefs are nearly unbeatable and were trying to open their latest Super Bowl title defense with a win, and proved what Detroit coach Dan Campbell has come to know in turning around the long downtrodden franchise.

“This is a resilient team,” Campbell said. “We’re built to handle some stuff.”

Now, everyone else knows it too.

Under the bright spotlight of the NFL’s season opener, Jared Goff threw for 253 yards and a touchdown, new Lions running back David Montgomery ran for the go-ahead score late in the game and Detroit held on for a 21-20 victory over the Chiefs.

“We expected to win this game,” said Campbell, who won just three games his first season but led the Lions to eight wins over their final 10 games a year ago, when they went 9-8 and narrowly missed the playoffs. “We came in here, knew what we needed to do, knew it wasn’t going to be easy, and we did that. We won.”

Amon-Ra St. Brown had six catches for 71 yards and a score, and Lions rookie Brian Branch returned Patrick Mahomes’ first pick in an opener 50 yards for another touchdown, helping Detroit snap the Chiefs’ eight-game Week 1 winning streak.

The Lions also snapped their own five-game skid in season openers.

“A lot of work has been put in this offseason,” Goff said, “and you want to start off winning the first one, and we did that today. We didn’t play the best on offense, I thought the defense kept us in the game, but we found a way.”

The Lions were trying to run out the clock when Goff’s fourth-down pass near midfield was batted down with 2:30 left, giving the Chiefs a chance. But they made a mess of it: Kadarius Toney dropped a potential 20-yard gain, a deep completion was called back for holding, Skyy Moore dropped a pass and a false start left Mahomes heaving a fourth-and-25 throw downfield.

When it fell incomplete and Detroit took over, Montgomery ran for a first down and the Lions ran out the clock.

Mahomes finished with 226 yards passing and two touchdowns, despite his receivers dropping a slew of passes. He also was the leading rusher for the Chiefs, whose self-inflicted wounds proved too much to overcome.

“Got to be better,” Mahomes said.

There had been equal parts anticipation and anxiety leading up to the game in Kansas City, where the Chiefs had celebrated their previous Lombardi Trophy in the midst of a pandemic, and only about 18,000 fans were able to join in the revelry.

Hundreds began tailgating outside the Arrowhead Stadium parking lots 14 hours before kickoff today, and NFL commissioner Roger Goodell along with about 80,000 more people joined them to see the Chiefs raise their latest championship banner.

That was the anticipation. The anxiety came from the absence of Chiefs tight end Travis Kelce and fellow All-Pro Chris Jones, who is in the midst of a contract holdout. The defensive tackle was expected to miss the opener, but Kelce had only been questionable since Tuesday, when he hyperextended his knee in the final full practice before game day.

“It wasn’t feeling right,” Chiefs coach Andy Reid said. “I wasn’t going to put him out there with that, and he was honest with me.”

Detroit scored first in a showdown of two of the league’s top offenses a year ago. Goff took advantage of a clean pocket, thanks in part to Jones sitting in a stadium suite, to march down field and find St. Brown with a 9-yard touchdown pass.

The Chiefs answered with Mahomes finding five different wide receivers on a long drive, the last of them rookie Rashee Rice, who atoned for an earlier drop by snaring a short touchdown pass to knot the game at 7-apiece.

It remained that way until Campbell made a questionable decision late in the half.

The Chiefs were facing fourth-and-2 near midfield but had been called for holding, and rather than decline it, Campbell chose to push them back. Mahomes responded to third-and-17 by hitting Marquez Valdes-Scantling with a 24-yard strike. He added a 26-yard pass to Justin Watson, then hit Blake Bell with a short TD throw to give the Chiefs a 14-7 halftime lead.

With the Lions’ offense still going nowhere in the second half, the defense stepped up. Branch caught a pass that bounced off Toney’s hands and found nothing but 50 yards of grass separating him from the end zone and a 14-all tie.

Up to that point, Mahomes had thrown 20 touchdown passes without an interception in five-plus season openers.

The Chiefs tacked on two field goals, but the missed chances to get into the end zone proved costly. The Lions followed up Harrison Butker’s second kick by driving 75 yards, twice converting on third down, with Montgomery capping the march with a 9-yard touchdown run that gave Detroit the the lead for good.

“The Lions did a heck of a job. They capitalized on a couple of things and we’ve got to fix it,” Reid said. “I liked the aggressiveness on the defensive side. There were some good things on offense. We just have to be more consistent.”

STREAK ENDS

The Lions’ Marvin Jones fumbled away a good scoring chance in the second quarter, when Trent McDuffie knocked the ball out deep in Kansas City territory. It was the veteran wide receiver’s first fumble in his 12-year career and came on his 563rd touch, the longest active streak in the NFL.

LATEST ON KELCE

Kelce had a bone bruise and some swelling in his knee, though tests taken after the injury in practice showed no ligament damage. He went through a workout early today to see whether he could move well enough to play, but Reid and Chiefs trainer Rick Burkholder decided to give Kelce time to recover with their next game 10 days away.

INJURIES

Lions: Branch, the first player with a pick-6 in his Lions debut since 1967, departed with cramps on the final play of the third quarter. … DT Levi Onwuzurike limped off with trainers with about 12 minutes left in the game.

UP NEXT

Lions: Play their home opener on Sept. 17 against Seattle.

Chiefs: Visit Jacksonville on Sept. 17 for a divisional playoff rematch.