The 49ers’ showdown Sunday night against the Packers at Levi’s Stadium is the most important regular season game they’ve played in nearly a decade.

Week 10’s Monday night tilt with the Seahawks carried plenty of weight with the once dormant rivalry coming back to life and NFC West implications, but the results of the rest of the Week 10 slate diminished some of the do-or-die nature of the contest. San Francisco lost, but stayed on top of the NFC and the NFC West.

They don’t have that same luxury Sunday night. Here’s what’s a stake with a win and with a loss.

With a win …

San Francisco stays on top of the NFC and the NFC West if they knock off the Packers on Sunday. It also pushes Green Bay to two games behind the 49ers with five to play. A win ensures they go into Week 13 in first place in the conference and division, regardless of what happens with the teams around them.

It would also get them to 10 wins, which doesn’t necessarily guarantee a playoff spot, but it puts them in a great position to secure a playoff berth early in the season.

With a loss …

There’s a scenario where the 49ers lose and stay atop the NFC West. Seattle would have to lose to the Eagles in Philadelphia, which isn’t out of the realm of possibilities. However, that would still push San Francisco to the No. 2 seed and give Green Bay the head-to-head tiebreaker with the 49ers.

A bigger, more nightmarish scenario, is the one where the 49ers lose and Seattle wins. That makes whatever the Saints do irrelevant because the Seahawks would jump over the 49ers in the division thanks to the head-to-head tiebreaker. That would move San Francisco to the No. 5 seed, which means they’d open the playoffs on Wild Card Weekend on the road. That’s a far cry from home field advantage throughout the playoffs and a first-round bye.