San Francisco 49ers vs Los Angeles Rams — Win Probability

San Francisco's 20-Point Upset Over LA Rams Exposes Model Underestimation

The San Francisco 49ers delivered a decisive 27-7 victory over the Los Angeles Rams on Sunday, a result that deviated sharply from both the model's pregame projection and the market consensus.

Before kickoff, the model assigned the Rams a 60% win probability and projected a Los Angeles victory by 3.4 points, with an expected final score of 26-22 Rams. The betting market aligned more closely with that view, installing LA as a 3.5-point favorite. San Francisco, by contrast, was given only a 40% win probability despite being the actual winner.

What actually happened was a complete reversal. The 49ers won 27-7, a 20-point margin that inverted the model's projection entirely. This qualifies as an upset: the Rams were favored by the market and the model, yet lost convincingly at home.

The magnitude of the miss is substantial. The model's expected margin of -3.4 (favoring LA) versus the actual margin of +20 (favoring SF) represents a 23.4-point swing. That gap indicates the model systematically undervalued San Francisco's ability to control the game, generating offense and limiting Los Angeles' scoring. The 49ers scored 5 more points than the model expected them to; the Rams scored 19 fewer.

This was not a close miss corrected by noise or variance—it was a fundamental mismatch between what the model projected and what unfolded on the field. Whether due to factors the model did not account for or a straightforward underestimation of San Francisco's advantage, the projection proved substantially inaccurate. The 49ers' dominant defensive performance and offensive efficiency were not reflected in pregame expectations.