Here’s an interesting one — when Vegas first released a “lookahead line” for this game back on May 13th, the Rams were 1-point favorites. Factoring in 3-points for home-field advantage (which in this case goes to San Francisco), a -1 spread implied the Rams were about 4-points better than the 49ers on a neutral field, at least in the eyes of oddsmakers.
Intuitively, that opening line made sense, since the 49ers were planning to proceed with a young, inexperienced QB in Trey Lance at that time; and youth doesn’t always fare well vs. fierce defenses like the Rams, especially early in season.
Fast forward to September 18th: unfortunately Trey Lance got hurt, Jimmy Garoppolo took over at QB, and oddsmakers pulled this game off the board. When it returned: the spread flipped from Rams -1 to +2.5; effectively a 3.5 point difference.
Which raises a question… Is Jimmy G really worth 3.5 points to the spread? According to Pro Football Focus (PFF), the answer is no, but it’s close: they estimate Jimmy G is worth about 2.5 points to the spread (roughly 1 point less than the revised line implied). Market forces seem to agree with PFF, as the consensus line has since tightened, with the Rams settling in as +1.5 underdogs. Compared to the original opening line, it’s a 2.5-point difference, which matches Jimmy G’s expected point spread value.
Now that the dust has now settled, I think it’s fair to say that any value on the spread has been squeezed at the current number. In simpler terms: the current line offered by sportsbooks is likely a fair one, with little to no edge on either side.