KANSAS CITY, Mo. -- The Detroit Lions marched into Arrowhead Stadium on Thursday night and upset the reigning Super Bowl champion Kansas City Chiefs, 21-20 in the NFL season opener.

Detroit Lions

The Lions went toe-to-toe with the reigning Super Bowl champions and came out ending the NFL's second-longest active winless streak (0-4-1) in season openers. Former Chicago Bears running back David Montgomery put the Lions on top for good with an 8-yard touchdown with 7:11 remaining, giving Detroit its first 1-0 start since 2017.

Promising trend: Amon-Ra St. Brown helped the Lions get off to a quick start with the game's first touchdown -- a 9-yard catch from Jared Goff with 2:46 remaining in the first quarter. Later, he became the first player in Lions history to reach 200 receptions in his first three NFL seasons with his fourth catch of the day. He's proven to be Goff's most reliable target since he joined the Lions in 2021 and that appears unlikely to change this season.

Buy on a breakout performance: Rookie defensive back Brian Branch scored on a pick-six in the third quarter. After receiving rave reviews from coaches and teammates all summer, the Alabama product became the first Lions player to score a defensive touchdown in his first career game since Louis Delmas in 2009.

QB breakdown: Goff extended his streak of consecutive passes without an interception to 359 Thursday -- the third-longest in NFL history. Goff looked comfortable against the Chiefs, completing passes to seven different receivers including new skill guys wideout Marvin Jones Jr., tight end Sam LaPorta and running back Jahmyr Gibbs

Next game: vs. Seahawks (1 p.m. ET, Sept. 17)

Kansas City Chiefs

Tight end Travis Kelce has 10 days to fully heal his injured knee before the next game. The Chiefs need him to use it wisely. The Chiefs sputtered on offense without him in the opener. Receivers had trouble getting open and dropped several passes, none bigger than the one Kadarius Toney deflected that was intercepted and returned for a touchdown. The result was the Chiefs' first loss in an opener since 2014.

Under the radar stats that matter: The Chiefs usually won't be defined by their rushing game, but they'll need more than they got against the Lions, at least until Kelce returns. Taking away Mahomes' scrambles, the Chiefs rushed 17 times for 45 yards, a meager outing for an offense in need of a spark without its top receiver.

QB breakdown: Mahomes was without his top receiver in Kelce, so he made do with the receivers he had. He completed passes to 11 different receivers and was at his best on a drive late in the first half. He threw a 25-yard pass to Rashee Rice to get the Chiefs near midfield, then threw 34 yards to Marquez Valdes-Scantling on 3rd-and-17 and 26 yards to Justin Watson. Those plays set up a 4-yard touchdown pass to Blake Bell that put the Chiefs ahead 14-7.

Eye-popping NextGen stat: The Chiefs weren't perfect with their pass rush without Chris Jones, but they were effective at times. Mike Danna had a third-down sack to end one drive and pressure from George Karlaftis forced an incompletion on another third-down play.

Next game: at Jaguars (1 p.m. ET, Sept. 17)