Kelvin Kuo-US PRESSWIRE
What is the Castrol Index, and how did Chivas USA players rank?
Soon we'll be beginning our 2012 player postmortems. Besides the usual player recaps, we'll be sprinkling in some statistics when we think it appropriate. One such stat will be the player's Castrol Index rating. I thought this might be a good time to explain what exactly the Castrol Index is.
Put simply: the Castrol Index--henceforth referred to as "the Index"--is a ranking system which, using Opta data, tracks and rates players based on whether a player's actions either help the team score or prevent conceding a goal. Each player gets a score and, from that score, a ranking.
Players are ranked from 1 to 470 and this year's scores ranged from Robbie Keane's 854 to 20 players who came in at zero due to playing such a paucity of minutes that it would be impossible to accurately assess their performance (ex. Marco Delgado played a total of 17 minutes on the first team this year). The Index has a specified baseline for minutes played each month--per their F.A.Q., it's approximately 60% of season game time. Players not meeting the baseline have their score truncated.
Though the Index is relatively new to MLS, the Index is by no means new, nor is it beholden only to American shores. Going as far back as 2008, some variation of the Index has been used in top European leagues, as well as the 2010 World Cup and both the UEFA Champions League and this year's Euros.
This year's results for MLS were very striker-heavy: only one player--Seattle net minder Michael Gspurning--is not a forward (for the sake of argument I'm including Kei Kamara as a striker even though he often played as a winger in Sporting Kansas City's 4-3-3--he did lead the league in shots after all).
Being a forward doesn't necessarily make you a shoe-in for a high score, though. In 2011, seven of the top 10 finishers were defenders.
With so many of the accolades going to the ones who fill the score sheet, Chivas USA landed just one player in the top 50 and it should be no surprise that it's Dan Kennedy. Kennedy is ranked 42 overall and placed sixth among goalies.
Something I found very interesting is how well Chivas USA player rankings correlated with their minutes played. There's a statistical test called Pearson's R--it tries to determine if there is a correlation between two sets of numbers based on a scale of -1 (a direct negative correlation) to 0 (no correlation) to 1 (direct positive correlation).
Running the test, I found a very high correlation of .89. In order to account for the small sample size (26 players), .89 far exceeds the .39 threshold to determine that it's statistically significant.
In laymen's terms, I can confidently say at least 95% that the highest ranking Chivas USA players were those who were on the field the most.
It quickly escalates into chicken-and-the-egg situation: did these players score so high because they were just on the field the most? After all, you can't improve on your score if you are stuck on the bench. Or did Robin Fraser tend to put the best team possible on the field?
It's worth noting that while Chivas player rankings correlate well with minutes played, that is not a trend beholden to the league in general. Several players--Kris Boyd (at number 15), Gspurning (11), Blas Perez (10), and Saer Sene (6) are all in the top 15 despite each missing at least 10 starts and--Gspurning excepted--having several teammates play more minutes.
- With this as our guide, it seems that the Goats' best centerback pairing is Califf and McKenzie who we didn't see play together after September 8th against the Seattle Sounders. Stop me if you've heard this one before.
- Strength of schedule is included into the calculations. I wonder how (or if) the results would be different had the league played a balanced schedule.
- *Players are rated for the whole season. i.e. players acquired midyear by Chivas USA have their pre-Chivas stats taken into account. In other words, Sharlie Joseph's rating is based on both his tenure at the New England Revolution as well as Chivas.