By Mark Asher Goodman (@rappidsrabbi)

It all started with Micheal Azira.

At the conclusion of the 2017 MLS season, I sifted through the wreckage of the Colorado Rapids awful season, player by player, to see what could be learned. Who, among these players was actually a high-quality soccer player? Who should the team retain for next year? Who should be jettisoned? Why? How can I know the difference? And, most importantly for readers of a data-obsessive website like American Soccer Analysis, can I find a credible way of answering those questions using advanced metrics?

For goal scorers, the answer to that question is, more or less, yes. You have expected goals (xG), and while flawed, it can tell you with a certain degree of reliability whether one striker can find the back of the net better than another. For passers, expected assists (xA) can be instructive, too. It can broadly inform a person as to whether a player gets a lot of passes into good spots that create goals. Both of these measures, xG and xA, are certainly reductive: they boil players down to just a few of their assets rather than measuring the totality of their contribution. Both of these measures are unable to isolate out a players individual contribution as completely independent of the actions of the whole team.

But the results you get from a table of xG roughly conforms to observations you make with your eyes. Josef Martinez is off the charts in his G-xG performance for 2017; he had an expected goals of 12.35 but scored a total 19 goals on the year, outperforming expectation by 6.65 goals. We still don't know if he's so good he breaks the model or just a bit lucky, but if you watched Josef Martinez in a game in 2017, you saw him score goals from blistering runs, incredible angles, and fantastic long blasts. Your eyes confirmed what the numbers tell you: Josef Martinez is a killer striker.

Surely, I thought, there is a way to do the same thing with defensive midfielders. Of course, I had to focus on the defensive midfielders. Because I have a serious thing for d-mids. If there was a ‘Unified Field Theory’ of soccer; if there was ‘one ring to rule them all’ for soccer enthusiast, writer, coach, and dad Mark Goodman, it would be ‘your defensive midfielder is the key to everything.’ So, back in November, I set about trying to assess the Rapids journeyman defensive midfielder and Ugandan international Micheal Azira by coming up with a unified metric that would assess all the d-mids in MLS. This attempt to create the ‘one big stat’ is not unlike how baseball created the metric VORP (Value Over Replacement Player) or how basketball uses OBPM and DBPM, (Offensive/Defensive Box Plus/Minus), or how throwball uses the QB rating.

I certainly put in a serious and thoughtful effort, and overall I was fairly pleased with how it came out. But even I can admit that the results were highly suspect. I’m really not a math guy - I took some college stats courses, and I’m a reasonably smart dude, but there isn't a lot of math in rabbinical school (thankfully). I’m a soccer guy, and so I used my philosophy of trying to find examples of what a soccer player playing as a defensive mid ought to be doing, threw numbers at it, ranked all the qualifying players, and came out with a chart. It’s not even a cool metric like how QB ratings are clustered around 100 or VORP establishes the baseline as 0.0 valued ‘replacement level player’, simply because I couldn't even begin to wrap my head around how the hell I would go about that. So it’s just a simple ranking.

Before I show you the results, here was my thinking in selecting the statistics I used to find the ideal defensive midfielder. A defensive midfielder needs to clean up and shield the defense. They do that by either knocking the ball away from a dribbler (a ‘tackle’), kicking or heading out an errant pass (a ‘clearance’), stymieing a shot (a ‘block’), or stepping into a passing channel and coming away with the ball, (an ‘interception’). These four stats, taken together, form the core of what a d-mid does when he or she acts as a defender. On offense, I only want my ideal d-mid to do one thing - send in dangerous passes that might create a goal. Long passes, short passes, crosses, through-balls - it makes no difference to me. Send in a ball; break the lines; unlock the defense. The best statistic for this is ‘Key Passes’. I took those defensive numbers, marked ‘em CBI+T, added them up, and divided by the number of games a player played. I looked up those numbers for very defensive midfielder in MLS, along with a few central midfielders that I thought could be adequately described mathematically as defensive midfielders. And I ranked them all. Then I took all the players Key Passes per game. And I ranked all those dudes by key passes. Then I averaged those two sets of ranks. And behold, the perfect, not-in-any-way flawed or biased, entirely definitive, list of MLS defensive midfielders, from best to worst.