Well that was a disaster, didn't watch the game, can someone summarize what happened? was weather a factor?
I watched it all because across the 7 leagues I'm still alive, most of the games' notable players were meaningful to me.
I honestly can't even really describe it. The rain was a notable factor in the first half and it did seem to impact Stafford as he struggled to complete passing with more than ~10 air yards. Further, the Niners contained the run pretty well so the Rams' offense from last week was really stifled - though it made sense in the moment. In the second half, the Niners' defenders looked naturally more tired, the Rams did a nice job sticking to the run and speeding the game up (which hurt all players' overall fantasy productions), and while Kupp oddly disappeared Puka looked like his normal badass self and between him and Kyren they kept long drives going with consistent positive plays.
The Niners' side of things is really inexplicable. I thought Purdy (who I started in my most meaningful - a dynasty superflex) actually looked fine in the first half despite the 90 yards. He looked more accurate than Stafford in the rain (though he did get lucky as he threw two bad balls that defenders dropped) and his Wrs dropped 2-3 passes and he had a deep shot to Kittle that could have been either caught or PI called. So, at half, Purdy looked nonetheless "fine" to me from a fantasy perspective. Then after the rain let up at the start of the second half, Purdy looked just awful and, as I stated above, the Rams did a nice job burning up clock. Purdy's only and best chance of the half resulted in a pretty bad pick in the end zone (though Jennings - who objectively had a bad game with drops and running bad routes - looked to have maybe done something on the play Purdy didn't expect). The Niners' morale also looked terrible as they had some defensive injuries, that Campbell guy refused to play, and the Rams' long-ish drives were probably demoralizing.
I wouldn't panic on Purdy as I think he's been very good this year and the variety of factors going into that half (Thursday game, rain, drops, injuries, low morale) can't be attributed directly to him, but that second half was the worst football I've seen him play. I think it can be chalked up to just a bad night (which even the best athletes have), but national stage combined with this being being the first round of playoffs in many FF league - this one stings and will be memorable.