The Detroit Lions we're used to would have folded on Thursday night. More accurately, the old Lions wouldn't have been competitive in the first place. They wouldn't have even been asked to start the season against the defending champions, but that's another story.

The Lions trailed in the second half of the NFL's season-opening game against the Kansas City Chiefs. Detroit's offense was stuck. On the other side Patrick Mahomes was playing like the best player on the planet yet again, even without Travis Kelce. And it would have been reasonable if the Lions faded away, took their loss and looked forward to easier competition.

But these aren't the Lions we're used to. The team that hasn't won a division title since the 1993 season got some key defensive plays, finally got the offense going with the run game on a clutch fourth-quarter drive and pulled off the first upset of the 2023 NFL season, beating the Chiefs 21-20. They watched the Chiefs make crucial mistakes down the stretch, the type of errors the Lions usually make.

Kansas City didn't have Kelce, who is injured with a bone bruise after hyperextending his right knee in practice this week. The Chiefs were also without star defensive lineman Chris Jones, who is holding out. It's hard to win in the NFL without two of your three best players, and there's no real shame in the Chiefs losing Thursday night.

The opening game might have said way more about where the Lions are going. One game into the season, the Lions have already made a huge statement.

Lions get back in it on big play

The Lions played a good first half. A gutsy fake-punt call from their own 17-yard line led to a touchdown and a 7-0 lead. Detroit moved the ball fine, getting 188 yards before halftime. But Marvin Jones Jr. fumbled in field-goal range. The Lions couldn't stop Mahomes on a two-minute drill late in the half. Kansas City scored in the final minute and a pretty good half for the Lions turned into a 14-7 deficit with the Chiefs getting the ball first to start the second half.

It seemed like the Chiefs would take control of the game early in the second half. Then Kadarius Toney helped out Detroit.

Toney dropped a pass over the middle that hit him right on stride, right in the hands. The ball bounced right to Lions rookie defensive back Brian Branch, who made a nice catch and took off for a 50-yard touchdown. The game was suddenly tied.

A massive audience had tuned in to see the first game of the NFL regular season, between the defending champs and a fun upstart. Branch's big play turned it into a competitive one. Anyone taking the history of the Lions and Chiefs into account and expecting a Kansas City blowout haven't been paying enough attention to what Lions head coach Dan Campbell has been building.

Lions take a late lead

The Lions were back in the game on Branch's interception return touchdown, but they couldn't take advantage. Detroit's first three drives of the second half ended in punts. The Lions' defense was doing its part, holding the Chiefs to field goals, but the offense couldn't get much going. The Lions held the Chiefs to a field goal after Mahomes slid a little too soon on a run, setting up a second-and-1. Detroit didn't allow a first down after Mahomes was short of the first down. Harrison Butker's second field goal of the game gave the Chiefs a 20-14 lead early in the second half.

The Lions needed a big drive right then. It was then they remembered they have a fantastic offensive line and some good running backs. Detroit started running it effectively. Jared Goff hit a few big passes. They went on a nine-play, 75-yard drive. David Montgomery capped it with an 8-yard touchdown run. The extra point gave the Lions a 21-20 lead.

Then the Lions' defense made another huge play. Inside of six minutes left in the game, the Chiefs tried a tricky jet sweep to Rashee Rice after a direct snap to tight end Blake Bell on third-and-1. Lions defensive end Josh Paschal wrecked the play and brought Rice down for a 3-yard loss. The Chiefs punted, and it became a possibility that the Lions were on the verge of an upset.

The Chiefs' defense made its own big play. The Lions had a fourth-and-2 just past midfield and went for it, hoping to put the game away. Safety Justin Reid knocked down a Goff pass and the Chiefs took over at their own 45 with 2:30 left. That's usually when Mahomes wins the game.

The Chiefs blew it after that. Toney had a massive drop on a pass downfield. New left tackle Donovan Smith got a holding call that brought back a long catch by Skyy Moore. Moore had a pass that was in his hands knocked out and it fell incomplete on second down. After a third-down incompletion, the Chiefs went for it on fourth-and-20. After a false start penalty, they decided to still go for it on fourth-and-25. That's long odds even for Mahomes, and a desperation pass was knocked away.

Montgomery put the game away by getting a first down on a third-down run.

As the Lions took a knee to kill the clock, there were audible cheers at Arrowhead Stadium from many Lions fans who made the trip.

The Lions had not won a season-opening game since 2017. Most years, their season was practically over before it started. Fans just hoped for a good showing on Thanksgiving. The offseason hype for Detroit was heavy after a good finish to last season.

For the first time since anyone can remember, the Lions might be worth the optimism.