Denver ? What, in the name of Dan Fouts, is going on here?

The Denver Broncos head into December facing a key game against a tough division opponent. That’s nothing new.

The opponent is the San Diego Chargers. That certainly is.

The Chargers are hot, at 8-3 and on a five-game winning streak, and the Broncos are the next team that’s going to have to deal with it.

Denver coach Mike Shanahan fielded a question about the last time he faced San Diego this late in the season with this much on the line.

After a long pause, he smiled.

“This is a setup, isn’t it?” he said.

But this is no joke.

The Chargers have the league’s second-highest scoring offense, a formidable challenge for a Denver defense that looked shaky last week. The Chargers have Drew Brees, the league’s third-rated passer, and he’s doing a lot more than when Denver beat San Diego, 23-13, in September. The Chargers have coach Marty Schottenheimer, and even that doesn’t seem like such an edge for the Broncos ever since John Elway retired.

Denver coach Mike Shanahan will lead his squad into a matchup Sunday with the upstart San Diego Chargers. Shanahan, shown Sunday in Denver, and the Broncos are accustomed to playing big games in the AFC West, but not against the Chargers.

Anyone doubting San Diego’s legitimacy should take a quick walk through the Denver locker room.

“That’s a good team. A team that’s gotten a lot better,” tailback Reuben Droughns said.

Of course, all players make the next opponent sound great no matter what their record. But with first place in the division and possibly Denver’s playoff survival on the line, and with what the Broncos just endured — an embarrassing 25-24 loss to the Oakland Raiders that dropped them to 7-4 — there’s little doubt they’ll take the Chargers seriously.

“It’s a big game,” Jake Plummer said. “You can’t make it bigger than it is. It’s not a playoff game, but could have a lot of playoff implications.”

This isn’t the first time that’s been the case this late in the season between the Broncos and Chargers. It just takes a long memory to bring it all back.

In the late 1970s and early 1980s, the teams fought for supremacy in the AFC West and the Chargers won more than their share of games.

Common were images of Fouts hooking up with Charlie Joiner for big gains against Louis Wright and Steve Foley — or Kellen Winslow reaching over cornerback Steve Wilson for touchdowns. San Diego was the place where Elway, in one of the more embarrassing moments of his young career, lined up under left guard to take the snap.

Before that, on the last day of the 1979 season, the Broncos played on Monday night at San Diego with the division title on the line. The Chargers won 17-7, Denver was relegated to a wild-card spot and was eliminated the next week.

The Chargers split the season series, but won a tiebreaker over Denver for the division title again in 1981. But slowly as the years went by, San Diego slipped while Denver stayed strong. The Broncos lead the overall series 50-38-1.

Contentious moments between the two have occurred during the past decade, but they’re hard to find.

In 1996, leading by 17 in the first half, Junior Seau taunted Elway and told him he was washed up. Fired up by that remark, Elway led a rally and the Broncos won easily, 28-17. Last September, the Broncos (inadvertently?) brought their white uniforms to sizzling San Diego for a road game when the Chargers wanted to wear white. The Chargers got mad. The NFL stepped in and let Schottenheimer pick his color when San Diego played in Denver.

In Southern California, they’re touting this as the biggest game since the Chargers went to the 1994 Super Bowl and lost to San Francisco.

“This is better than the team I saw at the Super Bowl,” said Shanahan, who was offensive coordinator for the 49ers that year.

Maybe it was Plummer, though, who summed up the oddness of the situation when he talked about the consequences and disappointment of last week’s loss to the archrival Raiders.

“We lost that game and we didn’t want to,” he said. “But we knew, either way, we were going to have to beat the Chargers.”

It’s been a long time since anyone in Denver has said that.