The 49ers’ playoff scenarios: Who’s No. 1 — or No. 5?

SANTA CLARA — Sunday night’s visit to Seattle represents a fork in the 49ers’ playoff path.

If the 49ers (12-3) defeat the host Seahawks (11-4), the NFC playoffs will go through Levi’s Stadium, where the 49ers will have home-field advantage as the No. 1 seed, along with a wildcard bye before the divisional round.

If the 49ers lose, they will be the NFC’s No. 5 seed and start on the road in the wild-card round at the NFC East champion, either in Philadelphia or Dallas.

Wait, a 12-4 record would only get you a No. 5 seed? Yep, just as it did in the 49ers’ last playoff appearance, six years ago, when they won at Green Bay and at Carolina before losing an epic, NFC Championship Game at ... Seattle.

A No. 6 seed was a remote possibility for this year’s 49ers until the Minnesota Vikings (10-5) locked that up by losing at home Monday night to yield the NFC North title to the Green Bay Packers (12-3).

So, who and when will the 49ers play in their first playoff game in six seasons?

As the No. 1 seed, they would open on either Saturday, Jan. 11 or Sunday, Jan. 12, against the lowest remaining seed, so either the No. 6-seed Vikings or the winner of the Seahawks’ wildcard game at the NFC East champion, Philadelphia (8-7) or Dallas (7-8).

As the No. 5 seed, the 49ers would open on either Saturday, Jan. 4, or Sunday, Jan. 5, against the NFC East champion. (The Seahawks can only win the No. 1 seed by beating the 49ers and having both the Green Bay Packers (12-3) and New Orleans Saints (12-3) lose Sunday at Detroit and at Carolina, respectively.)

So who will win the NFC East? The Eagles, having just beat the Cowboys on Sunday, can win the division by defeating the host New York Giants on Sunday. If the Eagles lose, the Cowboys can advance with a home win Sunday against Washington (3-12). Those games kick off Sunday at 1:25 p.m.

And how do ties factor into the equation? Shhh, we don’t talk about ties, not after 49ers coach Kyle Shanahan averted one and went for the win in an eventual Nov. 11 overtime loss to the Seahawks.

The 49ers have lost eight consecutive visit to the Seahawks’ CenturyLink Field (it was named Qwest Field prior to the 2011 season).