So this game is kind of important, huh? But does it deserve the classic and cliched "must win" title?
It's tough to answer, but if the Rams are going to have a legit shot the division, this game is about as "must win" as it gets. Shooting for the Wild Card, probably a more realistic goal, makes this an important game, although in that situation the Rams will still have the rest of the season to pick up the wins they need.
For a true "must win" the losing the game would then result in a absolute consequence of the Rams having no chance thereafter to make the playoffs or continue their season.
This game is more of a "damn well better win" situation. Winning this game carries a few implication for the Rams, they are:
1. Challenging for the NFC West
The '1' next to the '4' on the Rams record represents the Rams only loss, to San Francisco, a team from the division. A Seahawks win would give them a 4-1 record, and put them at first place in the division with Rams having then lost two games against NFC West teams. If the Rams win this game, they get a game and a half on the Seahawks AND hand that team its first loss of the season to an NFC West opponent.
2. Give the Rams legit status
All those sentences inserted by writers next to the Rams logo on their power rankings chart, you know the ones saying that they can't yet be considered a serious threat to make the playoffs, will all go away. If the Rams beat the Seahawks, especially if it's not a fluke win, the Rams join the field of NFC contenders...or at least the tier of teams below Chicago.
3. Padding for the win column
After their bye next week, the Rams have a really, really tough stretch of games to play. Getting a win this week would give them a little breathing room headed into games against San Diego, KC, Seattle again, Carolina, and an early December visit from the Bears.
There's three pretty good reasons for getting a win this week, on top of the usual things like, oh, pride and the fact that everyone likes winning much better than losing, etc. It may not be a "must win" in the lexicon of NFL hyperbole, but it's pretty close.