Run Lines Are Not Spreads (And That Matters)

Run Lines Are Not Spreads (And That Matters)

If you are coming from NBA betting, you are used to spreads that move in half-point increments across a wide range. A team can be favored by 1.5 or by 14.5. The spread reflects the expected margin of victory, and it moves fluidly based on money and information.

MLB run lines work differently. The standard run line is -1.5 / +1.5 for almost every game. Instead of adjusting the spread, the market adjusts the price. A heavy favorite might be -1.5 at -180 (you risk $180 to win $100). An underdog might be +1.5 at -120. The run line itself rarely changes. The juice does.

What This Means for Edge Detection

In the NBA, the model finds edges in the number: the market says -7.5 and the model says -10. The edge is in the 2.5-point gap. In MLB, the model more often finds edges in the price: the market says -1.5 at -150 and the model says that price should be -130. The edge is in the 20-cent gap on the juice.

> MLB edges tend to be more subtle. A 3.5% edge on a run line looks different than a 3.5% edge on an NBA spread.

Both are mathematically equivalent in expected value, but the run line edge requires more precision because the model is disagreeing with the market on probability, not on margin.

Moneylines

The MLB model also evaluates moneyline odds (straight win/loss, no spread). Some of our strongest edges may come on the moneyline rather than the run line, particularly in games with closely matched pitching. When you see a moneyline signal, the model is saying the probability of one team winning is meaningfully different from what the market implies. No spread involved, just pure probability disagreement.