By Dustin Nation (@D_Naish)
In a previous article, I looked at the effect of roster consistency on overall team performance. There were enough interesting trends in the data that I wanted to look a little closer and try to see if there is a “right” number of changes that teams should make on a week-to-week basis.
After looking at each squad’s rotation and how it affected their performance over the past three years, it makes sense to look at how changing lineups from one week to the next effected team’s performances in that week. That is to say, given a team’s roster changes from the previous week, how likely were they to perform well?
A quick note before we begin: as discussed previously, there are many reasons that teams would rotate players and, as such, simply looking at weekly squad rotation numbers doesn't paint the entire picture.
Let’s dive right in and take a look at each year.
Here you can see that in 2015, the most common number of changes that teams made from week-to-week was two, followed by three changes and one change. It makes sense that one to three changes is most common from observing the league, and as you’ll see, it is a pattern that holds true across all years evaluated in this article.
Interestingly, teams that made zero, one, or two changes in a week were more likely to have won than lost, but teams that crossed the line and made three or more changes were more likely to have lost than won. I’ll call that line the “magic number.”
Making two changes was again the most common number of changes in 2016, and again one, two, and three were the by far the most frequent. Overall the distribution of changes looked very similar to 2015.
The performance graphs, on the other hand, do not.
While the likelihood of winning dropped as more changes were made, there was a lot more turmoil between the likelihood of losing and drawing. There was also not a defined grouping in zero to three changes like there was in 2015. Teams that made two changes in 2016 were actually more likely to lose than win, and teams that made three changes were more likely to win or draw than lose.
The “magic number” where teams were more likely to lose than win moved to at least four lineup changes per week.
The distribution of changes in 2017 was fairly similar to previous years. Despite one overtaking two as the most common number of week-to-week changes, one, two, and three, were still the most numerous number of changes in 2017.
Unlike previous years, the results for this year had no real “magic number” where teams who had higher numbers of changes were always more likely to lose than win. In fact, strangely enough, if you look all the way down to the right, teams who made nine changes were actually 2-0-0. In reality, that’s a very small subset of the total, so it’s probably safe to ignore it and declare the “magic number” for 2017 to have raised to five changes.
Also of note, 2015 and 2017’s likelihood of winning stayed above the likelihood of drawing (at least until seven or eight changes), while 2016’s likelihood of wins and draws swapped places at four and again at 6-8. That’s because 2016 had far more draws than the two preceding years.
Here’s the breakdown: