Kansas City, Mo. ? It was the season opener at the renovated Arrowhead Stadium, a marquee Monday night showdown between the Kansas City Chiefs and San Diego Chargers.

Played through driving wind and rain, the Chiefs hit San Diego with two long touchdown strikes and then stopped Philip Rivers in the shadow of the goal line four times in the final minute to preserve a 21-14 victory — one that spurred Kansas City to the AFC West title.

One that played a big role in ending the Chargers’ four-year reign atop the division.

“I think it gave us a lot of momentum and a lot of confidence going into the season,” recalls Chiefs cornerback Brandon Carr. “We knew going into that game last year that it was a great team we were going to face, a high-powered offense.

“They’d been running the AFC West for a long time,” Carr said earlier this week. “To go out there and play as hard as we did, and come up with a victory and have the crowd behind us the whole way, it was a confidence boost for us for the season.”

The Chiefs hope another Monday night showdown against San Diego, this time on Halloween night, will give them a similar boost the rest of the season.

“I think we’re taking steps in the right direction. I think everybody in there is excited about the opportunity we have in front of us on Monday night,” quarterback Matt Cassel said. “We’re up for the challenge and we’re excited about the opportunity again.”

Much has changed since that Monday night matchup last season.

The Chiefs are playing without Jamaal Charles, their All-Pro running back, who had a 56-yard touchdown run against the Chargers. He tore the ACL in his left knee and is out for the year.

But perhaps the biggest difference is the feeling in the Kansas City locker room.

The Chiefs had won 10 games total over the previous three years, but won 10 last season alone, and they enter this year’s matchup riding a modest three-game winning streak after a horrendous start.

“It was huge for us,” Chiefs coach Todd Haley said of last year’s game against San Diego. “Now, last year was last year and this year is this year, but when you start a season and you’re coming off a difficult season and you’re able to play a division opponent at home, on Monday night, on national television, and get off to a good start, it definitely gave us a boost.”

Such an admission is rare from Haley.

Under normal circumstances, the third-year coach would never put more emphasis on any one game over any other. He views the season in four-game quarters, each as important as the next.

“It was one game in a series of four that we like to stay focused on,” Haley said. “Now this is one game in a series of four that we’re really focused on, and we know that last year has nothing to do with this year. We’ve got to go out there and play our best football.”

Norv Turner said the same thing, nearly word for word, about the Chargers playing their best.

The Chargers coach said last season’s opener, in some ways, set the tone for their season. They wound up losing five of their first seven games, and although they turned things around quickly enough to finish 9-7, it wasn’t enough to overtake Kansas City in the division.

“Well, we went through a lot of things early in the year that were apparent in that game,” Turner said. “You see no Vincent Jackson, no Marcus McNeill, and we had some other issues. We had a lot of things going on for the first 4-5 weeks. But that was an unbelievable evening.

“You start the game and it was a very nice evening and midway through the second quarter or whenever it started, the temperature dropped, the wind, the rain,” Turner recalled. “It was like you went from August or early September to late November in about a half an hour.”

This time, the two teams will be meeting on the doorstep of November.

The stakes are perhaps even higher.

San Diego (4-2) has a half-game lead in the AFC West, but the Chiefs can forge a three-way tie with the Oakland Raiders if they win tonight.

In doing so, they can become the first team since the Pittsburgh Steelers in 2000 to start a season 0-3 and then win its next four games.

“They haven’t lost since we played them last,” Rivers said. “This game is obviously big for both teams. Division games are huge. They almost count as a game and a half. It’s one of the loudest stadiums you ever play in. You’ve got to manage that.”

Rivers remembers just how difficult it was to manage last year.

“You watch that tape and it doesn’t quite show the conditions and how crazy it was. That was for both teams,” Rivers said. “Certainly, weather was a factor for both teams and they handled it better than we did. The thing I remember is we had some false starts and delay of games that hurt us. I’ve got to do a better job of that. And four downs inside the 5 at the end with a chance to tie it up.”

A chance the Chargers frittered away on an electric Monday night.