DFS Correlation Explained: Why Stacks Work

By Splash Play Staff · A guide to reading the tools

Correlation in DFS means two players' scores tend to move together. A quarterback and his receiver are correlated because one play scores for both: every completion is passing yards for one and receiving yards for the other. Stacking them widens your lineup's range. When the passing game works, you get paid twice. When it doesn't, you lose twice.

Where correlation comes from

From shared events. Fantasy scoring gives points to more than one player for the same thing.

NFL: a touchdown pass scores for the quarterback and for whoever caught it.
MLB: a hitter who reaches base can score a run when a teammate drives him in; the teammate receives the RBI.
NBA: a game that runs fast and close lifts the numbers of players on both teams.

Correlation can also be negative. Two running backs on the same team split the same carries, so more for one usually means less for the other.

What a stack does to a lineup

It changes the range, not the average. Two made-up players, each with the same projection whether you pair them or not: put together two who rise and fall together and the lineup's good nights get better and its bad nights get worse. Put together two who offset each other and the lineup's scores bunch toward the middle.

The arithmetic, for the curious: the spread of a pair is each player's own spread plus a term for how they move together. With made-up variances of 9 and 16, the pair comes to 31 if they move together a little and 19 if they move against each other by the same amount. Same two players by projection, a very different lineup.

Why that matters

A wider range is what a large tournament pays for, because the prize money sits at the top and an average score wins nothing. It is not what you want where half the field cashes and you only need to beat the middle. A stack is a tool for a kind of contest. It is not a free upgrade.

What a stack costs

Salary. The pair may leave you weaker somewhere else.
Concentration. One bad game sinks two roster spots.
Company. Obvious stacks are popular, so when they hit, many other lineups hit with you.

Two players from the same team are not automatically a good pair. The link has to run through plays that score for both of them.

In the tools

The Portfolio Builder lets you set a primary stack mix, then shows the completed percentages before you export. In NFL Classic the stack types are a quarterback with one, or with two or more, of his own pass catchers, each with or without a bring-back from the other team. In DraftKings MLB they are five-man, four-man and scattered. FanDuel allows at most four hitters from one team, so the platform limits still apply. These controls do not apply to Showdown. Change the stack rule and nothing else when you compare two builds. If you also changed the player pool, you cannot say which change moved the result.

The Portfolio Builder is part of Apex, for NFL and MLB. Open the NFL tool for the current slate, read the field guide for the step-by-step workflow, or compare memberships. Correlation explains how a lineup's range is built. It does not promise the top of it.