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Intermediate MLB DFS: ISO

We continue our breakdown of the basics for MLB DFS. In this section, we look at ISO, with definitions and some basic strategy.

Nelson Cruz #23 of the Minnesota Twins follows through on a third inning home run against the New York Yankees in game one of the American League Division Series at Yankee Stadium on October 04, 2019 in New York City. The Yankees defeated the Twins 10-4. Photo by Jim McIsaac/Getty Images

In daily fantasy baseball, like in most things, getting the fundamentals down is integral toward laying a foundation of knowledge to build from as you progress as a player. For DFS, that means understanding how the ISO statistic can help you build your lineups.

Stolen bases


ISO, or Isolated Power, is calculated as slugging percentage minus batting average. It’s much simpler than wOBA, but in its simplicity it gives us a great view of the best power hitters in the league.



The league average ISO is around .140. Anything above .170 is good, while anything below .100 is bad. In DFS, power numbers convert into DK points at a much higher rate than walks, singles and runs scored, so finding strong matchups for high ISO performers is key.

GPP vs. Cash

ISO numbers are useful across the board but if you want to win a GPP, you must have good power numbers accumulate across the board. ISO is the best predictive statistic for power numbers long term, which means it is the best to use when evaluating hitters for DK upside. If you are playing in a cash matchup, ISO isn’t the statistic to rely on. You want a little more safety and will want players who can get on base more often. If that player also has a good ISO, that’s great, but not the most important.


Checking splits on any statistic is a step you should take in evaluation. As a basic rule, right handed hitters see the ball better against left handed pitchers and end up putting up better statistics against them and vice versa. For some batters it is more pronounced than others and in some rare cases a batter bucks the trend and hits better or at least equally against pitchers of the same “handedness.”

Extreme cases, where ISO is much higher or lower against a lefty or righty, may push that hitter to see fewer at bats when a different handed relief pitcher comes in, but as long as the matchup is strong against the starter, you are still maximizing your matchup.


Pitchers also have an ISO statistic, but it is based on what hitters accomplish against them. Basing performance on ISO will help you find pitchers who don’t give up many extra base hits while also helping you find pitchers who do. Look for the extremes on a slate and you can find the best pitchers to face, especially in GPPs.


We can’t be assured that a pitcher will face a certain number of lefties or righties in any matchup, but we can see how many lefties vs. righties each team sends out in their average lineup. Some teams are going to be stronger against one side of the plate than the other and if your pitcher matches up well against a lineup based on splits, you are in business.

Sample size

If you have a player with multiple years under his belt, looking at his statistics should be predictive as to how he will play moving forward barring injury. We can see how he’s been progressing or not, from year to year and then see how his current yearly statistics stack up to his career statistics.

Small sample sizes aren’t to be trusted, especially if they go against a steady career norm. The good news is that we can see minor league stats as well, so even rookies have some history to evaluate, but quantifying numbers against major league hitting and pitching is always the most useful.