The National Football League's 2023 regular season got underway with a shocking result as the Detroit Lions defeated the reigning Super Bowl champion Kansas City Chiefs 21-20 at the Chiefs' Arrowhead Stadium on Thursday night.

Lions wide receiver Amon-Ra St. Brown scored the first touchdown of the new NFL season late in the first quarter on a 9-yard pass from quarterback Jared Goff.

Two-time MVP Patrick Mahomes and the Chiefs came roaring back, scoring two unanswered touchdowns to take the lead 14-7 heading into halftime.

Lions rookie safety Brian Branch picked off Mahomes and returned it for a touchdown early in the third quarter to tie the game.

Chiefs kicker Harrison Butker kicked two field goals, giving Kansas City a 20-14 lead until Lions running back David Montgomery found the end zone for the game-winning score with just over seven minutes to play in the game.

Mahomes, playing without star tight end Travis Kelce, who was ruled out with a hyperextended knee suffered at practice earlier this week, finished with 226 yards, two touchdowns and an interception. Goff finished with 253 yards and a touchdown.

"Played hard the whole game," Goff told the NBC broadcast after the game. "It was a long, hard game. We probably didn't play our best, but we are built for this. We really are."

It was an impressive win for the Lions, a team that has generally endured futility for decades, having not won a playoff game since the 1991 season. The Lions will hope they are turning around under third-year head coach Dan Campbell, who last year guided the team to a winning season -- 9-8 -- in which Detroit won eight of its final 10 games.

It wasn't all bad for the Chiefs on Thursday. Prior to kickoff, the team unveiled its latest Super Bowl champion banner to a nice ovation from the Chiefs faithful.

The Lions will host the Seattle Seahawks next week while the Chiefs travel to Duval County to face the Jacksonville Jaguars in a rematch of last season's AFC divisional round playoff game.