Published: 15 January 2016
One of my recent goals is to operationalize the lessons that football analytics has provided. It’s one thing for these ideas to end up on a blog post somewhere or get retweeted a bunch of times, but it’s another thing to turn the research into actionable information. And it’s yet another thing to put it into action. For example, having a Win Probability model is cool and everything, but it was only a bunch of numbers until teams starting using its related applications to inform their decisions.
So I’m always most excited when I have a new tool to unveil. The AFA Draft Trade Evaluator Tool
is now live and is currently available to all readers. The tool calculates the total value on each side of the trade, allowing users to judge the merits of any proposed deal. In truth, it’s not so new because there are a bazillion other tools and charts available
—my personal favorite is Chase Stuart’s widget at Football Perspective
based on Doug Drinen’s excellent Approximate Value
metric from Pro-Football-Reference.com
But the AFA tool brings some new things to the party, some awesome things. It evaluates trades based on three separate models simultaneously—the conventional Jimmy Johnson chart, the Approximate Value model, and the Massey-Thaler surplus value model.
Plus, the AFA tool is the only tool to consider time
. When a trade involves picks from future years, it calculates the implied discount rate needed to make the trade fair in all three models. This is essentially a measure of how much a team is borrowing from the future to gain draft value in the present. Think of this as the annual interest rate you’d be willing to pay if you were putting a draft pick on your credit card. Very high rates are bad for borrowers (teams trading away future picks) but are good for lenders (teams trading away present picks).
Here’s how it works:
It’s set up like most of the other tools at AFA, with an input area on the left and a result area on the right. Enter the pick numbers on both sides of the trade, along with whether each pick is in the present year (Yr0) or in future years (Yr+1 or Yr+2).
Then just click calculate, and the results will show up on the right. The results are divided up into three sections, one for each of the models: Johnson, Approximate Value, and Massey-Thaler. For each model, the draft value on each side of the trade is totaled for each year. The total value for all years is summed up. If there are picks from years +1 or +2 involved, the tool will calculate the discount rate implied by the trade for all three models.
This was a fun and challenging project because calculating the discount rate is not a simple matter of crunching a simple formula. For anything beyond a simple one-year scenario, you have to solve a quadratic or cubic equation (or whatever you call equations with exponents greater than 3…). Quadratics are ok--we all learned how to solve those in 7th grade. But cubic equations are nasty hard. I had to build my own numeric solver, kind of a custom version of Excel's Solver
or Goal Seek
plug-ins. Brute force wins the day.