The new NFL season began with an upset as the Detroit Lions put down an early marker by beating the Kansas City Chiefs, 21-20.

But what did we learn from the game about the Lions' prospects for success this year or the status of the reigning NFL champions?

Lions can tame the NFC North

It's always risky to make snap judgments for the season ahead based on Week 1 results, but Thursday's Lions victory feels like a significant step forward for the franchise.

Rejuvenated quarterback Jared Goff fired darts to an exciting group of receivers while protected by a solid O-line and running backs that recognized when the Chiefs were blitzing.

The defense did a great job too and the sort of mental errors that plagued the Lions for many years have been gradually ironed out by Dan Campbell and his staff.

Campbell has turned around the team's fortunes in a relatively short amount of time, as it is worth remembering that Detroit were in possession of a 1-6 record after eight weeks of the 2022 season.

The Lions have shed their reputation of being a doormat for other teams to trample all over and are now a destination for winners, which is more or less what safety C.J. Gardner-Johnson has been saying since his defection from the NFC champion Philadelphia Eagles in March.

Detroit, who are +105 to win the NFC North title, can next look forward to hosting the Seattle Seahawks - the team that pipped them to the final NFC Wild Card berth last season - at Ford Field.

If the Lions win that game and the following week's home game against the Atlanta Falcons, and the Lions will be going into their first divisional game of the year in Green Bay with a 3-0 record for the first time since 2011.

Kelce cannot return soon enough for Chiefs

All of Kansas City will be hoping the extra few days the Chiefs get before their Week 2 game against the Jacksonville Jaguars help Travis Kelce heal up in time to play.

The tight end, who hyperextended his knee in practice on Tuesday, sat out his first NFL game because of injury since his rookie season and was badly missed by his teammates - particularly Patrick Mahomes.

The big target has often been a comfort blanket for his quarterback during clutch moments in Mahomes' stellar career.

Mahomes completed 10-of-22 (46%) passes to his wide receivers on Thursday and it was noticeable that when he would usually be targeting Kelce with the game on the line, he was throwing to guys that he had less chemistry with or who were having bad nights.

In his postgame comments to the media, Mahomes sounded as though he was desperate for Kelce to return in Week 2 when the Chiefs are -150 on the money line to return to winning ways against the Jaguars.

Not an impressive return for Nagy

The tight end was not the only missing piece in Thursday's game from last year's Super Bowl-winning team, however, with offensive co-ordinator Eric Bieniemy having moved on to fulfil the same role in Washington.

Matt Nagy stepped up to retake the position he relinquished in 2018 when he took over as the Chicago Bears head coach, but he did not slot seamlessly back into the role.

It may take some time for Mahomes and the Chiefs offense to get on the same page of the offensive playbook that Nagy brought with him to Arrowhead Stadium,

However, the attempted trick play on the crucial third-and-1 that Lions lineman Josh Paschal blew up behind the line of scrimmage should be headed for the trash.

After a bright start, Mahomes struggled when the Lions made adjustments at halftime.

He completed just three of his first eight pass attempts in the second half and that was when the alarm bells should have been ringing for Nagy to make some changes of his own.

Mahomes did work with the returning OC as a rookie backup in 2017, but Nagy could not lift him out of a passing slump down the stretch underscored by a dismal second-half stat line of 9-of-22 for just 79 yards and a QB rating of 32.2.

New bookends on Chiefs O-line excel

The performance of Kansas City's two new offensive tackles came under some scrutiny after both were responsible for costly penalties on the Chiefs' final drive.

But overall, the performances of Jawaan Taylor and Donovan Smith were encouraging in protection against some very good pass rushers.

Former Jaguars star Taylor won enough of his battles with Aidan Hutchinson on the right, while Smith produced some flashy plays as he stepped into the void created by Orlando Brown's offseason move to the Cincinnati Bengals.

He was perhaps harshly called for the hold that cost his team a crucial late first down.