SAN FRANCISCO (AP) — A December matchup between fierce rivals that only months ago looked to be a for-sure NFC West championship decider has instead become San Francisco’s chance to show it still belongs in the playoff mix. Period.

If the two-time reigning division champion 49ers (8-4) can’t beat the Seahawks (11-1) at home  Sunday, they will certainly have a far more daunting task of trying to beat them in Seattle if the teams meet again in the NFC playoffs.

“If this doesn’t fire you up, if this doesn’t fire up the fans, then what does?” 49ers coach Jim Harbaugh said. “I suppose Abraham Lincoln riding across the field with a frock and a top hat, riding a horse, waving an American flag. I doubt that would fire them up, if this game doesn’t fire them up. The people that really love football would be fired up by this matchup.”

Seattle clinched the NFL’s first playoff berth with a rout of New Orleans on Monday night, and could wrap up the West and first-round bye with a win at Candlestick Park.

The Seahawks are thinking far beyond the rivalry, or that a team that reached the last Super Bowl is on the other side.

“Well, we’ve been in the midst of these for a long time,” coach Pete Carroll said. “We’ve looked at every game like it’s a championship opportunity for us, and we’ve continued to see and feel it that way.”

Here are five things to watch Sunday in Seattle’s final visit to Candlestick Park:

San Francisco’s 12th man

The 49ers are calling for a “red out” this weekend, as in all fans wear red. Anything to help boost the energy at Candlestick for a game of this magnitude.

Sure, the Niners would love to establish a home-field advantage similar to what Seattle has.

“I would hope for that this week, that Candlestick, we get it cranked up,” Harbaugh said. “Make it a real great environment, because it’ll be a great football game.”

Not that Seattle isn’t accustomed to noise. The Seahawks’ own home games help them prepare — and on Sunday they will try for a franchise-best sixth road victory.

“Our crowd is sensational,” quarterback Russell Wilson said. “They’re so loud every week. So, yeah, I think it definitely does. We’re not afraid to go on the road and play in a tough environment.”

Bragging rights
in the West

Sure, Seattle has owned this series of late, outscoring the 49ers 71-16 in the past two meetings, both at home. Yet that hardly matters with the high stakes on this one.

“It’s a new game, another Sunday,” 49ers linebacker Patrick Willis said. “We’ve talked about it the last couple of weeks that every game we play from here on it out is important. It’s important to where we go to get into the playoffs. ... Once we get in, then I feel like anything can happen.”

The Seahawks don’t doubt it. They have had a good view of the Niners’ success the past two years since Harbaugh came aboard.

“They’ve been winning for a long time. That just makes it that much more of a challenge and difficult to get,” Carroll said. “We’re going for it with everything we’ve got this week.”

The December stretch

Carroll just chuckles at the idea that, as well as Seattle has played, people are concerned about the Seahawks peaking too soon to sustain this level of success.

“I’m glad people are concerned about that; we’ve been trying to manage a steady ascent in our play, our execution,” he said. “This is fourth quarter of the season, this is when you finish it off and set yourself up for postseason. We certainly haven’t gotten to the point we think we’ve got it made, we’ve got ‘em now.”

Wilson draws praise

Harbaugh doesn’t have enough good things to say about Wilson, and the 49ers coach has one of football’s talented young quarterbacks himself.

“He’s a little bit quicker than some defensive linemen, I guess,” defensive end Justin Smith said of Wilson. “I’m one of them.”

That MVP talk for Wilson, 49ers defensive coordinator Vic Fangio calls it “legitimate.”

“He’s a fantastic player. A wonderful, wonderful player, competitor,” Harbaugh said. “Skills of arm talent, mobility. Great field awareness. Understands the scrambling lanes, the escape routes out of the pocket. A lot of wonderful qualities about him.”

Seattle secondary

With a healthy receiving corps at last, the 49ers hope they have enough options to keep that trash-talking, big-play Seattle secondary guessing. Might it be Anquan Boldin, Vernon Davis, Mario Manningham or Michael Crabtree who Colin Kaepernick looks for downfield?

“Obviously the passing game was really on this last weekend,” Carroll said.

With Crabtree back for his second game since returning from May right Achilles tendon surgery, Kaepernick feels good about his options. And, perhaps, about quieting Richard Sherman, Earl Thomas and the rest of the defensive backs.

“I think you have to earn that every Sunday,” Kaepernick said of the confident chatter. “And this Sunday we’re going to make them earn that.”