I use a lot of sabermetric measurements when constructing my previews. and sometimes I use statistics that might not be easily understood. I think it’s safe to say that most baseball fans understand how stats like ERA, batting average, on base percentage, and slugging percentage work. Then there’s the more esoteric statistics; things like xFIP, BABIP, wOBA, stats that a lot of baseball fans might not care about initially but are very good at helping us see how a player is performing and, more importantly, how he is likely to perform in the future. There are also stats that I’m still learning about that we’ll take a look at in these features. That way we’ll both be learning something!
Today we’re going to look at one of my favorite pitching metrics: BABIP, or Batting Average on Balls In Play. Over a course of one season in baseball, about 30% of balls in play fall for hits. This means that, on average, a pitcher’s BABIP will rest somewhere between .290 and .300 when all is said and done.
There are three things that go in to every at bat where a ball stays in the park (remember, balls that don’t fall in play don’t count for BABIP! Not even home runs!): defense, talent level, and luck. Ichiro has a better chance of running down a hard fly ball to deep right than J.D. Drew. Troy Tulowitzki is gonna make a throw to first base more than Marco Scutaro. Simple. Talent level changes over the season. A pitcher could start hanging his slider or tipping a pitch, and until he makes necessary adjustments, his BABIP is going to be higher than normal. Luck sometimes just doesn’t go the way you need it to. Bloops can fall, grounders can dribble, these things happen.
The important thing to remember is that BABIP will always regress to mean. It may take a whole season for a pitcher to figure out what’s wrong, but high BABIPs don’t get posted regularly. It’s just how the stat works. This is useful because when I look at a pitcher like Roy Halladay (his BABIP is at .303 right now) I know that there isn’t going to be a drop in his numbers without some bad breaks. Roy Halladay is pitching as well as he does on any random day; when I look at Josh Beckett, however (his BABIP is at .217) I know there are some rough days ahead. That’s an unsustainable BABIP which means his performance measurements will drop. Higher ERA, higher WHIP, etc.
Things to remember about BABIP:
– BABIP is mostly a measurement of a pitcher’s defense and luck, not skill
– BABIP is a great way to see if a pitcher had an artifically inflated (or deflated) ERA for a season. Just compare the players BABIP to the league average BABIP or his BABIP for the past three years and you can see whether or not they’re due for a regression.
– Ground ball pitchers have a better BABIP on ground balls than other pitchers, and a worse BABIP on fly balls.
– The formula for BABIP is: (Hits – Home Runs)/(At Bats – Strikeouts – Home Runs + Sacrific Flies)
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