KANSAS CITY, Mo. — The Detroit Lions are going to be a problem. Not just this season, but for years to come.

David Montgomery scored the game-winning touchdown on an 8-yard run with 7:06 to play as the Lions beat the defending Super Bowl champion Kansas City Chiefs on their banner-raising night at Arrowhead Stadium, 21-20, on Thursday night.

Montgomery ran for a game-high 74 yards on 21 carries and picked up the game-clinching first down late in the fourth quarter, and the Lions got massive contributions from a slew of young players they expect to be the core of their future.

Brian Branch returned a Patrick Mahomes interception 50 yards for a touchdown. Jack Campbell made a diving pass breakup two plays earlier in the third quarter. Sam LaPorta had the key block to usher Montgomery into the end zone on his touchdown run. Jahmyr Gibbs finished with 60 yards from scrimmage. And second-year linemen Aidan Hutchinson and Josh Paschal led a much-improved Lions defense that held Kansas City to fewer points than it scored in all but three games last season.

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Hutchinson, last year’s runner-up for NFL Defensive Rookie of the Year, had three quarterback hits while providing relentless pass rush, and Paschal made a key tackle-for-loss on a third-and-2 trick play that forced a late Chiefs punt.

Paschal broke through the line to stop Rashee Rice for a 3-yard loss on a jet sweep from the Chiefs’ 34-yard line after tight end Blake Bell lined up under center for a direct snap.

Bell was playing in place of All-Pro Chiefs tight end Travis Kelce, who hyperextended his knee in practice Tuesday and was inactive Thursday.

The Lions won a season-opener for the first time under Dan Campbell, and, in the process, spoiled the Chiefs’ celebration on banner-raising night, doing so in front of a raucous crowd that had large pockets of fans wearing Honolulu Blue Lions jerseys.

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At times, the sellout crowd erupted into chants of, “Let’s go, Lions.”

The Lions, winners of nine of their past 11 games dating back to November, scored the game’s first touchdown Thursday on a 9-yard Jared Goff pass to Amon-Ra St. Brown, 10 plays after converting a fake punt deep in their own territory and mustered little offense most of the rest of the game, until they needed it, down six points with 12 minutes to play.

Montgomery started a drive that began at the Lions’ 25-yard line with a 5-yard run and the Lions covered 70 yards in their next eight plays to get in the end zone.

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Goff was 22-for-35 passing for 253 yards for the Lions and Josh Reynolds added 80 on four catches, including two key grabs for first downs on Montgomery’s touchdown drive.

Mahomes finished 21-for-37 for 226 yards with two touchdowns and his first ever interception in a Week 1 game. The reigning NFL MVP was hurt by a handful of drops from his receivers.

The Chiefs, who twice settled for field goals after long drives in the second half, had won eight straight openers, tied for the fifth-most in NFL history, and 16 straight games against NFC opponents.

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The Lions host the Seattle Seahawks in their home opener on Sept. 17 at Ford Field.

Contact Dave Birkett at dbirkett@freepress.com. Follow him on Twitter @davebirkett.

This article originally appeared on Detroit Free Press: Detroit Lions make big statement, beat Chiefs in K.C. in opener, 21-20