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Beginner’s Guide to Sabermetrics: K%, BB%, K%-BB%

May 12, 2015


FantasyPros has put together a glossary of sabermetrics statistics for readers to reference. Deeper statistical analysis is being used by fantasy players more and more in daily and season-long leagues. We’re providing the glossary so that you can easily reference what the stats we use in our articles refer to and how they should be used for fantasy baseball purposes. Below we’ll take a look at K%, BB%, K%-BB%.

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Strikeout rate (K%) and walk rate (BB%) are measurements of how often a hitter will walk or strike out per plate appearance. It is represented as a percentage which should make it easier to compare different players and years. It can be used to evaluate hitters, pitchers, and even team performance. The calculations are simple, all you have to do is divide strikeouts (Ks) or walks (BBs) by the number of plate appearances (PA). Like many stats, K% and BB% can be compared to the league average when evaluating performance, but it must be noted that league average K% and BB% will vary from year to year.

For hitters, K% and BB% is a good way to see a player’s performance at the plate. A player with a high BB% suggests that they have a good eye at the plate and can get on base even if they aren’t hitting for a high average. Players that get on base at a high rate obviously have a better chance to score runs or steal bases, if they have the ability. Walk percentage can also give you a good idea of the kind of approach a hitter has. Usually, a hitter with a good BB% is only swinging at pitches they can drive for hits. Strikeout percentage measures the rate at which a batter strikes out and like walk percentage, gives us an idea of the type of approach used by the player.

A player with a higher K% might get away with this rate because they are trying to drive more pitches, which can provide home runs, but also more strikeouts. A strikeout isn’t the worst type of out, so an elevated K% shouldn’t immediately be viewed as a negative, but if a player has a high K% and not the power numbers to back it up there should be a cause for concern.

An increasingly common way to evaluate pitchers has been to subtract their K% from their BB%. Since a pitcher is (mostly) completely in control of these two rates, it gives us a good idea of how well a pitcher controls the game on his own. Pitchers with consistently high K%-BB% rates are usually the best in the league, because they strike out batters at a high rate, and walk them at a low rate. Some people like to use BB% and K% for pitcher analysis since they account for the fact that some pitchers will face more batters per inning. Instead of using two metrics to show this, they have been combined to form K%-BB%. You can use K%-BB% to determine a pitcher’s approach, just like hitters. A high rate will tell us that the pitcher throws a lot of strikes and can make a lot of outs with strikeouts and his defense, and that the pitcher is stingy with walks allowed.

Finally, team K% and BB% can be useful for fantasy players, especially when streaming. It’s easy to sort team strikeout percentages and find match ups that can be exploited. There are many instances where a pitcher having an average season can have an above-average outing against a team that strikes out at a top-10 rate. Each match up will be different, but it is a good rate to use when making streaming decisions.

JP Gale is a correspondent at FantasyPros. To read more from JP, check out his archive and follow him @gojpg.

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