By Kurt Bullard

In baseball, it is taken as a given that players who hit for power tend to strike out at a higher rate than those who make their living off simply reaching base. A common metric used in portraying this phenomenon is the HR/K ratio. However, this statistic is relatively narrow – home runs are not an all-encompassing measure of power. For most players this statistic is relatively random; home runs are not a very frequent occurrence.

Instead of trying to measure strikeout rates against home runs, I’ll attempt here to measure it against ISO (Isolated Slugging Percentage). Isolated slugging percentage is a more representative measure of power, because it incorporates doubles, triples, and home runs, rather than just round-trippers. The question that I’m trying to ask is simply the following: how much power do you need to justify striking out at a certain rate?

To answer this question, I took the 153 players with the highest BABIP (batting average on balls in play) as of the first week of September. Then, I found the strikeout rate and the Isolated Slugging Percentage (TB-H/AB) of these players. Then, using Stata, I created a regression model that predicts, based on a player’s strikeout tendency, the player’s expected ISO. The more a player strikes out, the more power he should hit for, so we’d expect a positive correlation between the two statistics.

The program popped out the following regression model that had an adjusted R-squared value of .77:

*.092 + .342(K%) = Expected ISO*

Having this model, you could then find the residual of each player (Actual ISO/AB – ISO/AB) to see which players, for their given strike out rates, hits for the most power per AB by seeing who has the highest residual.

**10 Greatest Outperformers of Expected ISO, Given K%**

Name | K% | Expected ISO | Actual ISO | Residual |

Edwin Encarnacion | 15% | .145 | .293 | .148 |

Victor Martinez | 6.8% | .116 | .240 | .124 |

Jose Abreu | 22% | .166 | .277 | .111 |

David Ortiz | 16% | .145 | .252 | .107 |

Nelson Cruz | 21% | .164 | .239 | .106 |

Jose Bautista | 15% | .143 | .291 | .096 |

Chris Carter | 31.3% | .199 | .267 | .092 |

Mike Trout | 26% | .18 | .266 | .087 |

Giancarlo Stanton | 27% | .184 | .237 | .082 |

Anthony Rizzo | 12% | .134 | .211 | .077 |

Some familiar power hitters jump to the top, including Giancarlo Stanton, Jose Abreu, and Chris Carter. Two Blue Jays also make the list, with Encarnacion topping everyone and Bautista only 4 spots behind. But there are also some players with low strikeout rates—namely Victor Martinez—that have hit for less power, but have struck out less than other traditional power hitters.

**10 Greatest Underperformers of Expected ISO, Given K%**

Name | K% | Expected ISO | Actual ISO | Residual |

Derek Jeter | 13.5% | .139 | .050 | -.089 |

Chris Johnson | 26% | .181 | .099 | -.082 |

BJ Upton | 30.3% | .196 | .121 | -.075 |

David Freese | 25.7% | .180 | .106 | -.074 |

DJ Lemahieu | 17.7% | .153 | .082 | -.071 |

Elvis Andrus | 14% | .140 | .070 | -.070 |

Casey McGehee | 13.9% | .140 | .072 | -.068 |

Yunel Escobar | 11.5% | .132 | .064 | -.068 |

Zack Cozart | 14.5% | .142 | .075 | -.067 |

Leoyns Martin | 19.9% | .16 | .096 | -.064 |

It probably surprises few people—and validates this method of calculating conditional power—that Derek Jeter ranks last. So does BJ Upton, who, despite ranking fourth in strikeouts, ranks 108^{th} in ISO. No true power hitters fell into the bottom ten, which makes sense, since better power would probably hit enough home runs and doubles to keep themselves out of the bottom 10.

One limitation of this study is that it does not account for park size. There is not an adjusted ISO stat available that I was able to find or determine. However, since this stat incorporates all extra base hits, it will probably be less influenced by park size than is the HR/K ratio, in which distance from home plate to the fence is a bigger factor.

In short, using this method to determine the percent of at-bats with ISO is more far-reaching than the traditional HR/K statistic. While HRs in general are subject to luck and location, doubles, triples, and home runs tend to create a more well-rounded stat. Now it’s time for Chris Johnson (it’s a little to late for Jeter) to learn a little about hitting for power from Edwin Encarnacion.

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