Kansas City, Mo ? Not everybody gets handed the keys to a team that won 18 games the year before.

When Matt Cassel bolted off the bench for an injured Tom Brady in New England’s 2008 opener, he was living a quarterback’s dream. Humming, purring and rolling along, the Patriots were a nearly perfect football machine compared to the mess he found when he got traded to Kansas City.

It was instant football culture shock. Where Cassel and the Patriots won 11 games in 2008, the woeful Chiefs won two. In the three previous seasons combined, they hadn’t won 18.

Where he’d known stability in New England, Cassel found constant flux in K.C.

The offensive line did not compare. Neither did fan support.

And if he needed time to reflect on all that, he had the entire fourth quarter of last week’s game. Cassel, K.C.’s quarterback of the future, was on the sideline watching the end of a 44-13 rout by Denver because coach Todd Haley took him off the field.

It was purely a temporary demotion, Haley insists. An older, wiser and humbler Cassel will be back under center today against Buffalo.

“I think I’ve matured a lot over this season,” Cassel said. “I like the saying, ‘Adversity leads to advancement,’ and there’s a lot of adversity going on right now. It’s been tough at times.”

The Chiefs (3-9) play host to Buffalo (4-8) in a game that means almost nothing to anybody not directly involved. For Cassel, it’s an opportunity to regain the momentum and confidence that’s been lost the past two weeks by getting outscored by 60 points.

“You just keep moving forward,” he said. “Two weeks ago we came off two straight wins and everything was great. Now we’ve lost two straight, pretty handily, and everybody’s trying to figure out what we’re doing wrong.”

Making his fourth start for the Bills is Ryan Fitzpatrick, another young quarterback who’s found the sledding tough. Fitzpatrick and interim head coach Perry Fewell are both hoping to make a good enough impression to get their jobs on a permanent basis.

“We’re out there playing for each other, playing for our teammates and also playing for ourselves,” Fitzpatrick said. “Everybody is playing for jobs, and that’s kind of what you have to do as a football player, you have to go out there and play as hard as you can every week because it’s being put on film and it’s really a job interview for you.”

Cassel and Fitzpatrick have both known success against their opponent this week. Fitzpatrick quarterbacked Cincinnati to a 16-6 victory in last year’s regular-season finale, while Cassel was 2-0 in 2008 against the Bills.

Both are also coming off tough losses. In a setback to the New York Jets, the Bills were 1-for-11 on third-down conversions.

“But we have to move on from that one,” Fitzpatrick said. “We were making some strides and we had a couple games where we thought we were making progress and we certainly took a step back.”

Win or lose, the Bills might make a little history Sunday in Arrowhead Stadium. Wide receiver Terrell Owens needs to catch six passes to become the sixth man in league history with 1,000 receptions.

“Honestly, the thing for me, my body of work that I’ve had throughout my career, it kind of speaks for itself,” Owens said. “Those things don’t even register. Honestly, I didn’t know where I was as far as the receptions or anything like that. I just go out and play and try to make the best of my opportunities.”

One big difference since Fitzpatrick took over the offense is Owens being more involved. Twenty of his 43 catches and 407 of his 690 yards have come in his past four games.

“It looks like he’s running with the football very well,” said Haley, who was Owens’ receivers coach in Dallas. “He’s got a complementary receiver on the other side who creates some problems. It looks like he’s playing at a high level. He’s always a threat to score anywhere on the field.”

Haley won’t say if he’ll be quick to haul Cassel off the field again. But it would help if his surrounding cast would play better. The Chiefs have given up 40 sacks, second most in the NFL, and dropped a league-leading 37 passes.

It might be enough to make a guy long for the good old days.

“You look at any successful quarterback throughout the history of the NFL and I think they’ve got a good team around them,” Cassel said. “In football, it’s not a one-man sport by any means.”