Tuesday, April 30, 2013

The Kangaroo Score

The Kangaroo Score was something I came up with while trying to identify NFL Draft prospects that could become successful pass rushers.  I have seen other people who have used a similar method, but mine still has the honor of having the goofiest name.  So, I win on that point.

The score largely comes from a prospect's vertical jump and their broad jump.  Of course, not all jumps are equal.  A player weighing 200 pounds with a 36 inch vertical jump, simply isn't showing the same power or explosiveness as a 250 pound guy with the same jump. My solution was to multiply a players weight by their jump,  find what the average result was, and the see how many standard deviations a player's score was from that average.  It's just a simple way of gauging a player's lower body power.  We can extrapolate from this a simple mass times velocity equals force view of things, with the jump being used as the measure of velocity, to estimate the amount of force a player could generate against his opponent.  So, basically, I look at players as human projectiles.

For some positions, like defensive tackle, this could be seen as a measure of the power that they are generating when the ball is snapped..  It's sort a general test of an athlete's quick twitch muscles, and their overall explosiveness.  For defensive tackles this measurement alone is more than adequate to identify prospects, but I'll generally refine things a bit further.  As you move outwards from the defensive tackle, and a player's mass decreases from defensive ends to linebackers, to safeties, and finally to cornerbacks, you start to see agility become more of a factor.  The way I see it, a player (at any position, but in this case a pass rusher), could either explode through or past his opponent, or try to evade/work around them.  So, as their mass decreases it becomes more important that the player's score in the agility drills (short shuttle and 3-cone)go up.  Ideally a player would do well in all these categories, but that is somewhat unusual.  Continuing with the human projectile idea, you could compare a guy with a high Kangaroo score to a depleted uranium round fired from a tank, while a guy who also has a good agility score is more like a heat seeking missile.  Hmm, this human projectile idea is sounding more and more idiotic with every word I type.

Sticking with defensive tackles for a minute, let me add this.  While this explosiveness might be all that you need for a nose tackle, who can satisfy a team's expectations by simply being fat and immovable, the more their agility score goes up the more likely they are to create at least some pressure on the quarterback.

Here are some noteworthy defensive tackles and what their scores look like:

Player              Kangaroo Score            Agility Score
Haloti Ngata         2.043                            -0.645
B.J. Raji               1.478                            -0.531
Jay Ratliff              0.821                            1.530
Ndamukong Suh   0.900                            1.227
Geno Atkins          0.793                            1.056

On the other hand we have these guys, most of whom were highly drafted, that are entering bozo/failure territory (at least for their draft position):

Player              Kangaroo Score              Agility Score
Terrence Cody      -1.242                            -1.864
Torell Troup          -0.481                            -0.158
Glenn Dorsey        -1.466                            -0.188
Kentwan Balmer   -0.245                            -0.451
Justin Harrell          0.041                             -0.343

In Justin Harrell's case people might argue that he failed because of constant injuries, but I suspect there was little upside there to begin with.

The bulk of the players fall somewhere between these two groups, so evaluating them becomes a bit trickier.  My point is simply to suggest that such risky and subjective speculation should probably be reserved for the later rounds of the draft, and that high draft picks should generally conform more towards players who actually proved to be worth a damn.

Just for shits and giggles, I thought I would also throw out this score, though technically he is a 3-4 defensive end:
Player             Kangaroo Score                 Agility Score
J.J.Watt                 1.473                               2.347

Hmm, J.J. Watt, how can you not love those numbers?

Since I will probably refer to the Kangaroo Score somewhat frequently, I should probably mention something for the sake of clarity.  The Kangaroo Score for a player at one position generally shouldn't be compared directly to a player at another position.  This is because the score is a measure of how much they deviate from their peers at a particular position.  So, a linebacker with a 1.250 score may look good, but if he was dropped into the defensive tackle pool, he would get crushed, and his score would be much lower.

There are some other factors, such as college production, that I think are good to toss into the mix, but for now I just wanted to present a little bit related to the actual value of the NFL Combine.  People often want to dismiss its usefulness, but there is some important information that comes from it.  Later on I will try to show how some of these things relate to other positions (hmm, this was initially supposed to be about pass rushing 3-4 outside linebackers, but I got sidetracked).

Here are some links to different player positions, that illustrate the effects of the Kangaroo Score:
3-4 Outside Linebackers and 4-3 Defensive Ends
Athleticism and the Offensive Line
Athleticism and the Offensive Line pt. 2  Compares traits of  late round successes to highly drafted busts
'Big' Wide Receivers - focuses on Aaron Mellette, but illustrates the point.
Running Backs - talks about how the Kangaroo Score relates to being a 'power' running back
Athleticism and the Defensive Tackle -Compares the athleticism of successful DTs to busts.


  1. Are you aware that the 'raw' numbers (weight * vertical jump, weight * broad jump) are described by term of physics? That term would be *work*. Work is described in terms of energy. The SI units are newton-meters or Joules.

    1. Perhaps there are some interesting ways to think about combine measurables in terms of energy expenditure, or other concepts of physics for that matter.

      For instance, might a defensive player's reputation as a 'hard hitter' be in part due to his ability to generate a relatively large momentum transfer?

    2. You are correct, but I thought describing players in terms of newton-meters or joules might be a bit of a turnoff for most people. I actually had this debate with a physics geek family member at one point. It was partially a product of laziness on my part, and partially a feeling that the word "force" better conveyed the idea. Lazy physics, if you will forgive me for admitting to such a thing.

      I had contemplated doing a real measure of the peak velocity of each player's jumps, and perhaps converting the numbers to watts, or even god forbid, horsepower (how many Ndamukong Suhs do you need under the hood of your car), but I thought a simplistic view of things got the point across sufficiently.

      As for your "hard hitter" question, I think that is probably doable. We can certainly calculate player's velocities at a given distance, and we know how much mass they have, so why not?