Kansas City, Mo. ? If anybody knows how to win in Arrowhead Stadium in December, it’s Donnie Edwards.

Before he was a standout linebacker for Marty Schottenheimer’s San Diego Chargers, he was a standout linebacker for Marty Schottenheimer’s Kansas City Chiefs.

Edwards wore a K.C. uniform in 1996 when the Chiefs were just beginning a remarkable December home winning stretch which is now up to 19-1, including the last 17 in a row. He has experienced as both a Chief and a Charger the tricky winds and biting temperatures of Arrowhead Stadium in winter.

He’s seen how the howling sellout crowd deafens December visitors and imparts energy to the home team.

Nevertheless, his advice to his San Diego teammates coming in for a crucial Christmas Eve showdown is actually very simple.

“You’ve got to keep the crowd out of it,” Edwards said. “You take the crowd out and eliminate penalties and turnovers, you can win at Arrowhead.”

Neither team can nail down a playoff berth with a victory. But both could be eliminated by the end of the day.

For the Chargers (9-5) to get in, they must beat Kansas City (8-6) and then beat Denver on Dec. 31 – and have either Pittsburgh or Jacksonville lose at least once. If they become December victim No. 18 in a row in Arrowhead, the Chargers must beat Denver and have either the Jaguars or Steelers lose twice.

Kansas City’s odds seem even longer. The Chiefs have to beat San Diego this week and Cincinnati next week, both home games, and have Denver beat the Chargers, while Pittsburgh loses at least once.

A loss to San Diego means the Chiefs are denied the postseason for the seventh time in eight years.

“Our chances aren’t real good, but we know who we play Saturday,” said coach Dick Vermeil. “Right now, San Diego is playing probably like they were playing last week when they beat the only undefeated team in football. They might very well be the best team in the AFC right now.”

If momentum counts for much, the Chargers should be heavy favorites because they’re fresh off their finest game of the year, a 26-17 victory over Indianapolis that ruined the Colts’ dreams of an unbeaten season.

Since they dropped to 3-4 on Oct. 24 and Schottenheimer declared it a new season, the Chargers have lost just once.

“I’ll be honest with you, it has more to do with the people I have here than myself in terms of the motivation,” said Schottenheimer, who was 101-58-1 in 10 years as Kansas City’s coach. “We have really quality people here. Our ability to get them to understand the importance each week has been a very, very simple task.”

The Chiefs, in contrast, are reeling from a two-game road swing to NFC East contenders Dallas and the New York Giants that exposed serious flaws in their supposedly improved defense. They gave up more than 400 yards in each game. And the Giants’ Tiki Barber, splattering tacklers all day long, set a team record with 220 yards rushing.

Vermeil called the performance an embarrassment, an assessment none of his players could object to.

“I think we’re good,” said defensive end Jared Allen. “We had a setback. I think we’ve got something to prove.”

The game will also showcase some of the NFL’s best tight ends and running backs. Antonio Gates, who caught three touchdown passes in a 28-20 victory over Kansas City on Oct. 30, joined Kansas City’s Tony Gonzalez on the AFC Pro Bowl squad this week.

The Chargers’ LaDainian Tomlinson was chosen for the third time, while Larry Johnson, who leads the NFL in yards rushing and yards from scrimmage since Nov. 1, will be making his first trip to the Pro Bowl.

If they can’t stop Gonzalez and Johnson, the Chargers could have a tough time keeping the fans in their seats the way Edwards has urged them to do.

Schottenheimer, too, can appreciate how unkind Arrowhead can be to December visitors. It’s a subject he’s been quick to discuss this week.

“I told our football team the last time the Chiefs lost a (home) game in December, I was coaching there,” he said correctly.

“Maybe that’s why it happened. It’s a real challenge for our football team. With what’s at stake, I’m sure it’s going to be a tough, physical game.”