Foul Ball Rates and At-Bat Success: Significant Differences between Best and Worst Batting Averages


ball-copy.jpgIn “Is Fouling Off Pitches a Skill?”, Eno Sarris discusses the idea of the two-strike approach, asking in response to Sam Fuld’s questions about foul ball percentage, if the best hitters have some advantage at the plate as they face a two strike count. That’s the gist anyway. Sarris finds little evidence to indicate there is. But he and Fuld may have been looking at it all wrong.


Indeed, during the turn of the 20th century, many sources report that players had become adept at fouling off balls; this was before the foul ball actually counted as anything more than a dead pitch. Prior to 1900, in fact, players started becoming skilled at foul ball hitting in order to draw a walk. The historical data certainly impresses upon us that such a skill does exist.

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As is typical of baseball writers and statisticians, when we think of batting stats we always go to the defaults—batting average, WAR, OPS, etc. We also look at the number of at bats, runs and number of and how many hits. But we fail to consider the as important state of FABs (Fouls/At Bat). (Sarris used IncreaseFoul% for this analysis.). FAB (the percentage of times a batter gets on base via a BB, 1B, 2B, 3B or HR), however, as a statistic is as valuable as any of the others. And is the one that Sarris and Sam Fuld overlooked (mainly because I just made it up).

Looking at the top 10 averages from 2014 and comparing them to the bottom ten we see why the top players are so good. We forgot there’s a reason they are the top batters. FAB is the reason.

A quick peek at the numbers between Chris Davis, the 2014 player with the worst batting average after at least 400 at bats, and Jose Altuve, the best average, we see what appears to be a modest 25 foul ball difference. However, when we calculate the percentage of times Altuve gets on base with a non-intentional walk, a single, double, triple or home run versus Davis, we can see the true differences. Altuve is able to get on base 5.18% more often after hitting at least one foul ball than Davis.

This 5% difference between Altuve and Davis isn’t an exception; rather, it is the rule. Foul ball average conversation rates in 2014 between the players with the best and the worst batting averages were staggeringly different. Not only did the players with the best averages slap away more pitches for fouls per at bat, they had a considerably higher conversation rate for Unintentional Base on Balls, Singles, Doubles, Triples and Home Runs. It is this difference that helps make the best the best and the worst the worst. It is a pronounced 4.03%. This conversation rate would also partially account for the 800 additional at bats the top 10 averages saw last season.

Last season the ten best and the ten worst batting averages looked like this:
Best v Worst

What I’ve discovered in my research into FAB rates is that the top ten hit more foul balls with a conversion rate that is just over 4% higher than the bottom ten averages last season; that’s roughly 350 more times on base than the bottom ten. The top ten slapped away more fouls and converted more of those at bats:

Best v Worst Chart_Page_2  Best v Worst Chart_Page_1

There are a few probable reasons for this significant FAB difference, reasons that Sarris and Fuld overlooked:

    • The batters with the higher averages swing at closer pitches.
    • Top averages see more pitches as a result of swinging at closer pitches OR the setup of the system equates to more at bats naturally. This places the bottom of the order at a distinct disadvantage.
    • They are more skilled at—contrary to Eno Sarris’ conclusion—fouling off close pitches, just not necessarily in JUST a two-pitch count.

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In other words, slapping away pitches is a skill. The ability of the top averages, for whatever reason, to clearly be able to foul off more pitches at a consistently higher FAB. A noticeably higher rate of FAB indicates a skill. It’s no accident that the best are the best; they are able to shrug off more pitches than the lower averages in order to get to “their” pitch. This works to their benefit in many ways. The most obvious is they see more pitches as a result of their skill (yup; I am professing it a skill) in slapping away close pitches; this increases their odds of getting on base because they obtain a better understanding of pitch speeds and locations a pitcher is favoring. Fouling off more pitches also wears out the pitchers arm more quickly. Given that few teams have anything more than average bullpens, driving up the pitch count early in this era of 100 pitches is important. As I mentioned above, in the years before the foul ball became a 1st and 2nd strike and an out, guys had become rather adept at intentionally fouling off pitches. That ability is one of the main reasons the rule was changed. In some ways, I think the best batters of the modern era have developed a similar ability, though limited due to the first two fouls now counting as strikes and the potential for an out.

My advice for the bottom ten: If you even THINK it’s close to a strike, swing. The worse that can happen is nothing. Given that swinging at pitches drives up pitch counts, helps batters assess pitch types, speeds and locations better (take a “the more you see the more you understand” mindset), it can hardly hurt the averages of the bottom ten.

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Stay tuned for Part 2….