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DETROIT -- The Detroit Lions had a ho-hum attitude about the most lopsided regular-season win in franchise history.

Matthew Stafford threw two of his four touchdown passes to Calvin Johnson and Detroit routed the Kansas City Chiefs 48-3 Sunday, matching the 45-point win it had over Cleveland in the 1957 NFL title game.

Detroit broke its regular-season record set with a 44-0 win over the expansion Jacksonville Jaguars in 1995.

Lions coach Jim Schwartz claimed he wasn't impressed.

"We can play better," Schwartz said after shrugging his shoulders.

Detroit (2-0) looks as if it just might be the breakout team some expect this season.

The Chiefs (0-2) were expected to be competitive after winning the AFC West last season, but they're losing games and players at an alarming rate.

Kansas City running back Jamaal Charles was carted off the field midway through the first quarter with an injured left knee. A source familiar with the situation told ESPN NFL Insider Adam Schefter that Charles will likely miss the rest of the 2011 season after an initial diagnosis revealed a torn ACL in his left knee.

The source said Charles will have an MRI on Monday to confirm the diagnosis, but the team believes the Pro Bowl running back will not return this year.

Charles' injury further hurts a team already without Pro Bowl safety Eric Berry and tight end Tony Moeaki for the rest of the season.

"The season will not be canceled as far as I know," Chiefs coach Todd Haley said. "What we have to do is we have to stop doing those things that are costing us dearly, and putting us in very difficult positions."

The Lions led Kansas City 20-3 at halftime and 41-3 early in the fourth quarter after turning two fumbles into TDs, following up their season-opening win at Tampa Bay, in a home opener that didn't disappoint their fired-up fans.

"In the years I've been here, it is never been like that in the stadium," said center Dominic Raiola, whom Detroit drafted in 2001.

"We have to make sure this isn't like the Denver game. We blew them out like this, and we thought we had arrived, and look what happened."

Detroit dominated the Broncos 44-7 at home in 2007 to improve to 6-2 only to collapse with one win in the second half of the season, leading to the NFL's first 0-16 year in 2008.

Back then, though, the Lions didn't have a quarterback quite like Stafford or an assortment of playmakers on both sides of the ball.

He was 23 of 39 for 294 yards and four TDs -- one short of his career high -- and avoided mistakes after throwing an interception on the opening drive.

Stafford threaded a 15-yard pass to Johnson for the first score and put a pass where only Tony Scheffler could catch it on a 36-yard TD in the second quarter.

"They understand if they get a little seam, they've got a chance to get the ball," Stafford said.

Jahvid Best accounted for 123 yards and two scores. Johnson caught two touchdown passes for the second straight week and Nate Burleson had seven receptions for 93 yards.

The Lions went for touchdowns on a pair of fourth downs, one late in the third quarter and another with 5:05 left.

Schwartz insisted those decisions didn't have anything to do with the league ruling against Detroit and in favor in Kansas City on a tampering charge last season.

"We're not trying to do anything other than trying to win the game," Schwartz said.

Kansas City cornerback Brandon Flowers didn't think they Lions were trying to run up the score.

"This is the NFL," Flowers said. "We can't worry about who's trying to rub what in."

The Chiefs lost more than just the game, coming off a 34-point loss at home to Buffalo. Charles' exit left the team with Thomas Jones and Dexter McCluster in the backfield and without a player who ran for 1,467 yards last season.

"Even when Charles wasn't in the game, it appeared to me that we still had opportunities to make things happen and we weren't able to do that," Haley said.

Like the Lions, Kansas City set a record -- one it's not proud of after winning 10 games and the AFC West last season.

The Chiefs lost their first two games by a combined margin of 79 points, their worst scoring differential to start a season, according to STATS.

Matt Cassel was 15 of 22 for 133 yards with three interceptions and a fumble. Dwayne Bowe had five receptions for 101 yards, providing the only offensive spark the team had without its star running back.

Game notes

Detroit's Jason Hanson kicked two field goals in the first half, playing in his NFL-record 297th game with the same team. Hall of Famer Bruce Matthews played 296 games with the Houston-Tennessee franchise and Darrell Green was in 295 with the Washington Redskins. ... Lions TE Brandon Pettigrew had a shoulder injury. ... Kansas City lost the first two games of the 2007 season by a combined 27 points.

Information from The Associated Press contributed to this report.