Cardinals defensive tackle Calais Campbell reaches for Seahawks quarterback Russell Wilson in last year's game in Seattle.

SEATTLE – When two brothers grow up together, the older one is naturally the first to excel.

He is bigger, stronger, faster and sets the tone. Eventually, the younger one makes gains. The older brother dismisses the progress, cocksure that he is and will always be the dominant party, but the confidence burgeons within the little sibling.

At some point, the battle hits critical mass. Most of these scores are settled in backyards, but in the case of the Seahawks and Cardinals, the whole country gets to watch the drama hit its crescendo on "Sunday Night Football."

The Seahawks are the reigning two-time NFC champions and came within a yard last year of winning consecutive Super Bowls, which is why a 4-4 start hasn't fazed them. The Cardinals, though, have been on Seattle's heels for nearly two years now. With a 6-2 record heading into this matchup, they have a chance to seize complete control of the NFC West with a victory and shift the balance of power.

"These guys are standing in the way of where we want to go, ultimately," safety Tyrann Mathieu said. "But I'm sure we're standing in their way also."

The Cardinals left CenturyLink Field with a memorable 17-10 upset in 2013, but Seattle has won the other three games between these teams since coach Bruce Arians was hired. The Cardinals hoped to make their push last year, but the season-ending knee injury to quarterback Carson Palmer forced him out of both matchups. It was too much to overcome.

Now the roster is almost completely healthy – center Lyle Sendlein (shoulder) and wide receiver John Brown (hamstring) are the only starters questionable to play – and any past David and Goliath feel is absent. Following two weeks of hype, each side will enter with a peacock's strut.

"I think you'll have both teams with their chests sticking out," Arians said. "I don't think either one is lacking confidence in any form or fashion."

 "We're 6-2, so we should be the more confident team," Mathieu said.

Twice the Seahawks were in grave danger of losing their grip on the NFC West to the Cardinals last season, but they went into each game with the swagger that comes from reaching the pinnacle of the sport. They backed it up with their play, outscoring the Palmer-less Cardinals by a combined total of 54-9.

Seahawks cornerback Richard Sherman said the Cardinals are a rival because the teams face off twice a year, but puts them on the same plane as the 49ers and Rams. Arizona's recent ascension hasn't changed his perspective.

"It's the same size as it always is," Sherman said of the rivalry.

The Cardinals understand. For a team like Seattle atop the NFL hierarchy, it must absorb every other team's best shot.  

"Probably not on their side," quarterback Carson Palmer said of the rivalry talk. "I know they've had something going with the 49ers for a while. But it is (a rivalry) for us."

Seattle's thinking could change quickly with a loss – it would put the Seahawks three games back with seven to play -- and the Cardinals enter with the superior statistics. They are second in the league in scoring (32.9 points per game) and seventh in points allowed (19.1). The Seahawks have done a touch better defensively – giving up 17.5 points per contest – but the offense has struggled, scoring 20.9 points per game.

Seattle has played a tougher schedule and gets this one at home, where it has lost only three times in 27 games since quarterback Russell Wilson took over as the starter. The Seahawks have also been strikingly good at turning on the jets in the second halves of seasons, going 20-4 after the midway point the last three years.

The Seahawks have all the reason in the world to believe their dominance will continue. But little brother also has a right to think the tables have turned.

"The last couple of years, we always felt like we could beat these guys but they always found a way," linebacker Kevin Minter said. "It's time for us to find a way."