## Roto-Relevant Research: Home Runz

Whether we like our players to stroke dongs or jack taters, we all know our fantasy-based desire for the stat borders on the lecherous. The problem with the home run is that it’s such an I/O situation: it’s either a home run or it’s not. And using stats like isolated slugging percentage to try and suss out changes in a player’s power profile can be confounded by the fact that any ball that lands in the park is then subject to the interaction between the fielder’s grace and the batter’s speed. Doubles don’t always turn into home runs. Sometimes doubles are actually stretched-out-singles or boffed grounders in the outfield.

Are there peripheral stats for batters that can help us predict power surges? Or at least some numbers that can help predict which power surges will stick?

Maybe. It looks like Chad Young and Mike Podhorzer at RotoGraphs might have some interesting findings about batted ball distance and angle. By combining the two, the FanGraphs’ analysts are well on their way to a reliable expected home run per fly ball rate.

Actually they even found one, with a decent fit to what happens in real life:

xHR/FB = (-0.00845 * distance) + (0.00002 * distance^2) + (0.02125 * angle) + (-0.00043 * angle^2) + 0.61064

Given the fact that Jeff Zimmerman‘s site, BaseballHeatMaps.com, has a batted ball distance leaderboard with angles, the more earnest fantasy nerds among us can easily produce an xHR/FB. Then they could apply that percentage to the player’s fly ball rate — which has one of the better year-to-year correlations in baseball — and come up with an expected home run rate for the coming year. That number might even beat some of the numbers provided by more traditional projection systems.

But there’s an easier way to do this. Let’s say we are just interested in general directives when it comes to players that have shown power surges recently. Chad Young has some advice in that case:

1) We should expect most players to see a decline in distance year over year. Nothing huge, but two to three feet can make a difference.
2) A player who gains a big chunk of distance will likely keep about half that change, but this really only holds if the distance gained is 15 feet or more.

We have a benchmark! 15 feet of distance seems fairly significant in real life, too, so it passes the sniff test. Let’s see which players gained more than 15 feet of distance last season. In order to limit this to regulars, only players that hit at least 40 combined home runs and fly balls are on this leaderboard. And since we are interested in power hitters, anybody with an average distance under 275 was culled from the list — Jarrod Dyson may have added some punch, but nobody cares too much about three home runs versus two home runs.

Name stand count 2012 2011 DIFF
Chavez Eric L 51 296.3 254.7 41.6
Ruggiano Justin R 54 309.5 269.7 39.8
Carter Chris R 44 290.7 258.6 32.1
Alvarez Pedro L 82 309.5 280.6 28.9
Saunders Michael L 91 291.3 263.2 28.2
Hill Aaron R 154 283.8 256.9 26.9
Rios Alex R 137 285.1 260.2 25.0
Molina Jose R 41 280.5 256.8 23.7
Dunn Adam L 101 307.8 286.2 21.6
Desmond Ian R 101 291.9 271.0 20.9
Andrus Elvis R 86 280.0 259.1 20.8
Amarista Alexi L 52 275.8 255.1 20.7
Posey Buster R 102 300.8 281.0 19.8
Hamilton Josh L 127 306.2 286.6 19.6
Kubel Jason L 123 303.0 283.9 19.1
Gomes Jonny R 54 295.7 276.6 19.0
McCutchen Andrew R 121 306.1 287.2 18.8
Quentin Carlos R 76 300.4 281.8 18.6
Rodriguez Alex R 95 293.4 275.8 17.6
Pearce Steve R 40 278.1 260.8 17.3
Zimmerman Ryan R 104 296.6 279.9 16.6
DeJesus David L 107 287.4 270.9 16.5
Headley Chase L 72 303.9 287.5 16.4
Parra Gerardo L 62 300.9 284.6 16.3
Jones Garrett L 128 298.7 282.6 16.1
Iannetta Chris R 42 289.8 273.8 15.9
Moustakas Mike L 132 278.2 262.9 15.2

Another piece of the puzzle is age. Whether you believe power peaks at 25 — as I have found, although I did focus on ISO, which includes speed effects — or later, as others have shown, you’ll see that some of these power surges are more interesting than others. Eric Chavez, Jose Molina, Josh Hamilton, Jason Kubel, Jonny Gomes, Alex Rodriguez, Chris Iannetta and Garrett Jones are all on the wrong side of either of those numbers. Even Justin Ruggiano and Aaron Hill (both 31 this season) are on the downslope. Carlos Quentin is 30. Alex Rios is 32! Some of these guys don’t really have enough power to care too much about their inclusion here — Alexi Amarista and Elvis Andrus, I’m looking at you.

Chris Carter was platooned last year, and has too many whiffs to show a good batting average, but by this analysis, his power surge looks legit. Can he push Carlos Pena or Brett Wallace off a regular job and get full-time work this season? At least the Astros are a worse team than the Athletics — they can afford to give jobs to youngster just because they’re young and showing something. We always knew Pedro Alavarez had great power, so the only question is what his batting average will look like with HIS whiff problem. Michael Saunders fits in this same group — power finally surfacing amid strikeout concerns — but it’s nice to see him here anyway.

But maybe the most interesting group of players on this list are the youngest guys with the most to prove when it comes to their power. Ian Desmond, Andrew McCutchen, Chase Headley, Mike Moustakas and Buster Posey — these guys all hit career-highs, and all of them face questions (if to different extents).

Now there’s reason, perhaps, to believe this group of youngsters can provide encore performances this season and continue to slam salamis in the coming fantasy season.