Tuesday, January 19, 2016

Crude Team Ratings, 2015

For the last several years I have published a set of team ratings that I call "Crude Team Ratings". The name was chosen to reflect the nature of the ratings--they have a number of limitations, of which I documented several when I introduced the methodology.

I explain how CTR is figured in the linked post, but in short:

1) Start with a win ratio figure for each team. It could be actual win ratio, or an estimated win ratio.

2) Figure the average win ratio of the team’s opponents.

3) Adjust for strength of schedule, resulting in a new set of ratings.

4) Begin the process again. Repeat until the ratings stabilize.

The resulting rating, CTR, is an adjusted win/loss ratio rescaled so that the majors’ arithmetic average is 100. The ratings can be used to directly estimate W% against a given opponent (without home field advantage for either side); a team with a CTR of 120 should win 60% of games against a team with a CTR of 80 (120/(120 + 80)).

First, CTR based on actual wins and losses. In the table, “aW%” is the winning percentage equivalent implied by the CTR and “SOS” is the measure of strength of schedule--the average CTR of a team’s opponents. The rank columns provide each team’s rank in CTR and SOS:

Two things I always like to touch on is the CTR ranking of the playoff teams and differences in schedule strength. This season the playoffs perfectly selected the ten most deserving teams based solely on win-loss record and schedule. This usually does not happen due to strong or weak teams being bunched in particular divisions or the AL/NL disparity (more on why this was less of a factor in 2015 in a moment). However, the playoff structure was far from free of inequity as the top three teams in the majors all hailed from the NL Central, forcing Pittsburgh and Chicago into a one-game wildcard playoff while the weakest playoff team, the Mets, were rewarded with the NL’s #3 seed.

There is a fun bit of symmetry in this year’s strongest and weakest schedule. The strongest schedule belonged to Detroit. As we will see in a moment, the AL Central had a good year and vied with the East to be the best division in the AL. This year’s interleague divisional matchups were East-East, Central-Central, and West-West, so Detroit also had to face the NL Central juggernauts. Their SOS was 110, meaning their average opponent was about the quality of the Mets (CTR of 109).

The weakest schedule was that of the Mets. The interleague matchups with the AL East team didn’t hurt their strength of schedule, it was simply playing in the weakest division of the six that did. The division champion will typically have the weakest schedule in their division because their four divisional opponents by definition have the weakest possible W% that could be constructed from four teams in said division. So the Mets SOS was 90, which means their average opponent was about equivalent to the Tigers (CTR of 90). It also means that the average Tigers opponent would be expected to win 55% of games against the average Mets opponent.

The division and league composite ratings below are calculated as geometric rather than arithmetic averages:

I believe the NL East’s 77 is the lowest rating for a division during the six seasons I’ve published CTR. 2015 was the first time in that span that a NL division was the best in the majors, but the AL’s implied W% versus the NL has stayed strong (for the three years I’ve been using geometric averages it was .521 in 2013, .544 in 2014, and .531 in 2015).

I will next run through the ratings figured with three alternate inputs quickly with little comment. The first is based on game-Expected W%, which you can read about here. It uses each team’s game-by-game distribution of runs scored and allowed, but treats the two as independent:

The next set is based on Expected W%, that is Pythagenpat:

Finally, CTR based on Predicted W% (Pythagenpat using runs created and runs created allowed. Actually Base Runs. Which as we all know makes what follows worthless because this was “The Year That Base Runs Failed”):

I’ve also started including CTR based on actual wins and losses, but including the playoffs. The playoffs provide us with additional information about team quality even though the manner in which they do so is even more unbalanced than the regular season schedule. It is interesting to take a gander at it:

Even with St. Louis falling in four games in the NLDS and the Royals going 11-5 en route to the World Series title, the two Missouri nines finish in a dead heat on top of the ratings. Chicago really didn’t close the gap with the Pirates, their 0-4 NLCS undoing the gains that their 4-1 mark against their NL Central rivals in the opening rounds of the playoffs would have provided.

The teams sorted by difference between playoff CTR (pCTR) and regular season CTR (rsCTR):

The changes in ratings for non-playoff teams are all for AL teams to increase by one point and NL teams to decrease by one point due to changes in schedule strength. A few NL East teams weren’t affected at all, and neither were Texas, Toronto, and New York despite participating in the playoffs.