McVay
I know I know, it's only his first season ever as a HC, and he inherited a 4-12 mess from Fisher. And he's looked really appealing in preseason mostly, except for perhaps a few missteps regarding pulling Goff and interacting with the media re: Donald, but he looks very promising.
Hey, Austin Davis looked pretty promising too, a few preseasons ago!
But there is a slim but non-zero chance that McVay goes a hapless 4-12 again. IF it does happen, the narrative will surely be that he was promoted too quickly, he was too inexperienced, isn't ready yet, has a bright future down the road but not now, needs seasoning (whatever that means), etc. I don't know what the "number" is of wins he needs to keep the wolves out of the foyer, but I know he has to improve on Fisher's final year to be taken seriously. I don't think the Rams cut bait on him after 1 bad season, but LA fans are notoriously fickle and I do NOT want to play 2nd fiddle to the Chargers.
