The Seahawks have won four in a row on the road to start the season and have won nine of their past 10 against the 49ers.

But it was the last game in San Francisco that was the beginning or end of streaks — the 49ers’ 26-23 overtime win last Dec. 16 marked the last time the Seahawks have lost on the road in the regular season and snapped a string of eight straight wins for Seattle over the 49ers dating to 2013.

And now here the 49ers are again, at 8-0 the only unbeaten team left in the NFL with a point differential of plus-133 that is the second best (behind only the 172 of New England) and favored by six against the 7-2 Seahawks in a game that will go a long way toward determining the winner of the NFC West.

Here’s our weekly look at keys to the game:

MATCHUP TO WATCH

San Francisco’s defensive line against Russell Wilson and Seattle’s offensive line.

If the biggest statistical mismatch in this game is Seattle’s 25th-ranked defense against the 49ers’ seventh-ranked offense (in terms of yards per game) the most enticing is Seattle’s fourth-ranked offense against the 49ers’ top-ranked defense. And the key to it all for the 49ers is a defensive line that wreaks havoc, allowing San Francisco to get consistent pressure with just a four-man rush — San Francisco has the second-lowest blitz percentage in the NFL. But SF can get away with it because four of the 49ers’ defensive linemen have four or more sacks led by the seven of Nick Bosa as the 49ers have 30 overall, tied for third in the NFL. That’s in stark contrast to Tampa Bay, which blitzed roughly two-thirds of the time last week allowing Wilson to find lots of receivers open in man coverage and carve up the Bucs for 378 yards. But that’ll be harder to do against a 49ers defense that usually drops seven into coverage. Seattle has allowed 22 sacks this season, an improvement from a year ago when Wilson was sacked a career-high 51 times, due in part to steadier play up front and Wilson taking fewer chances. But this game will be an obvious challenge, especially with center Joey Hunt making his second start in place of the injured Justin Britt. Hunt played well last week but this will be his toughest game yet.

COACHING DECISION TO WATCH

How much nickel will Seattle play?

Seattle’s use of nickel packages — meaning five defensive backs — has been hotly debated of late with the Seahawks continuing to struggle in pass defense (Seattle 28th in yards allowed at 278.1 per game). The Seahawks have actually used more of it the past two weeks, with nickel corner Jamar Taylor on the field for 41% and 43% of snaps against the Falcons and Bucs (more than all but one other game this season). But the 49ers figure to have both of their starting offensive tackles — Joe Staley and Kyle McGlinchey — as well as fullback Kyle Juszczyk back for this game (Juszczyk hasn’t played since week 5) which might compel the 49ers to run even more, and might mean Seattle will want to leave its base defense on the field more often to combat a rushing attack that ranks second in the NFL at 171.2 per game.

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PLAYER TO WATCH

RB Chris Carson

While San Francisco’s pass defense has been among the best in the NFL this season, the 49ers have been more mortal against the run. The 49ers are allowing 4.7 yards per carry, more than all but five other teams in the league (and the same as the Seahawks). The argument in the Bay Area would be that a lot of those were garbage-time yards. But the Seahawks will take note that Arizona got 153 yards on 23 carries (6.7 per attempt) and try to replicate that with Carson, and maybe with some Rashaad Penny carries thrown in, as well, to not just help the passing attack but also shorten the game. Carson has been a steady performer all year with 90 or more yards in five of his past six games but has to curtail the fumble bug that crept up again last week.

THE X-FACTOR

WR Josh Gordon

Will he or won’t he play and how much? The guess here is that he will play, especially after showing in practice this week he is healthy (coach Pete Carroll said Saturday there is “a good chance” that Gordon will play, even if he might be somewhat limited in snaps after not practicing with the team until Thursday. Seattle could desperately use a reliable third receiving threat to go along with Tyler Lockett and DK Metcalf with tight end Will Dissly lost for the year. Even one big play or two could turn the tide in a game like this.

WILD-CARD PLAYER WHO COULD SURPRISE

PK Jason Myers

The patience of Seattle fans with Myers may have reached a tipping point last week when he missed two field goals and an extra point, including a 40-yarder on the final play of regulation that instead forced the Seahawks to have to win it in overtime. Myers is 12 for 17 on field goals and 24 of 26 on PATs. But Myers is also just a year removed from having made 33 of 36 field goals with the Jets and earning a Pro Bowl berth and the Seahawks are professing faith that he will turn things around quickly. Seattle could have a kicking edge in this game as the 49ers are likely to have to go with newly signed backup rookie Chase McLaughlin in place of injured veteran Robbie Gould. McLaughlin has made 5 of 7 field goals this season in a brief stint as an injury fill-in for the Chargers. He was the Big Ten Kicker of the Year last season as a senior at Illinois.

KEY STAT

65.7

That’s the passer rating allowed by the 49ers defense this season, second lowest in the NFL behind only New England. Wilson, meanwhile, leads the NFL with a rating of 118.2 that is also on pace to be a career high. He has had only one passer rating lower than 100 — 65.2 in a home loss to Earl Thomas and the Ravens. Now he faces another former Legion of Boomer, Richard Sherman, and what has become one of the best secondaries in the NFL. Something has to give and whichever side gets closest to its usual number here probably wins the game.

THE FINAL WORD

49ers 28, Seahawks 17

This is a real prove-it game for both teams. The NFL world is now accepting the 49ers as for real, while pointing out that San Francisco has beaten only two teams that currently have winning records (the Rams and Carolina, but having done so in impressive fashion, by a combined 51 points). Seattle likewise has gotten to 7-2 beating only one team that currently has a winning record (the Rams in a last-second thriller). What might be the most raucous home field edge the 49ers have had since moving to Santa Clara in 2014 will help SF draw first blood in the battle for the NFC West.