Wednesday, December 10, 2008

Cleveland Indians Sabermetrics 101: DIPS and RAR

In the last installment, we discovered that all pitchers' BABIP tend to fall in the .290 to .310. It follows then that if we want to gauge a pitcher's talent level, we need to look at everything besides balls hit into play. "Everything else" consists of strikeouts, walks, and homeruns, generally considered the "three true outcomes." There are a number of stats that study the three true outcomes, and together they are referred to as defense-independent pitching statistics - DIPS.

Before I go into examples of DIPS, I need to define a few terms.

replacement level: This is a popular concept among statheads. A replacement level player is one that is easily available as a mid-season free agent signing or a AAA call-up. Indians fans saw many replacement level players make starts for the Indians last year, Matt Ginter for example.

Runs Above Replacement, RAR: If "replacement level" is the amount of production you can get out of a player off the scrap heap, you would expect your regular players to be able to perform above that level. For pitchers, this means comparing the number of runs a pitcher gave up over a certain number of innings and comparing it to the number of runs a replacement player would have given up over the same number of innings. This is a tally of runs "saved" compared to a replacement pitcher, so a high positive number is better.

RAR for pitchers is calculated by taking the replacement level ERA, which is generally taken to be 5.75, subtracting the player's ERA, diving by 9 (since ERA is a measure of runs given up per 9 innings), and multiplied by innings pitched:

(5.75 - ERA) / 9 * IP

Wins Above Replacement, WAR: It's generally accepted in sabermetric circles that 10 runs is equal to 1 win. So, to find out how many Wins Above Replacement a pitcher earned, their RAR is divided by 10.


Beyond the Box Score's article on this topic covers many pitcher stats. I'll let you look through those at your own leisure. The most advanced is a new stat called tERA. It takes the three true outcomes mentioned above, plus HBP and percentage of hits that were ground balls, line drives, infield flies, and outfield flies, plus takes the ballpark into factor. With input that complicated, it has to be accurate, right? Well, you and I can just take their word for it for the time being.

Since the goal for many sabermetricians is to take luck out of the equation, StatCorner - the same people that created tERA - also created xIP, expected Innings Pitched. Put simply, xIP tries to determine what each play "should have been" (ie, a screaming liner that was caught is changed to a hit, and a blooper that dropped is changed to an out) to give a more accurate look at the pitcher's workload.

Indians RAR/WAR in 2008

How did the Indians fare in 2008?
Cliff Lee2222.64778
CC Sabathia122.673.26343
Fausto Carmona1214.64151
Zach Jackson573.81121
Aaron Laffey92.674.77101
Paul Byrd1285.4050
Jake Westbrook334.4050
Matt Ginter21.333.7650
Anthony Reyes324.7440
Scott Lewis234.5230
Jeremy Sowers1185.89-20
Bryan Bullington9.677.49-20
Tom Mastny1.6723.83-30
Total Result98279.13162.4516.24

As you can see, by this methodology Cliff Lee won eight games all by himself. Meanwhile, Matt Ginter, Bryan Bullington, and Tom Mastny were almost the definition of replacement level.

But that 162.45 total RAR means nothing without context. Cleveland finished fifth in the AL in RAR in 2008, just behind Boston and Tampa Bay, and just ahead of Anaheim and Minnesota. Toronto and the White Sox were almost 50 points ahead of their closest competitors, thanks to aces (Roy Halladay and Mark Buehrle) that scored in the 70s with a solid supporting staff. (Halladay and AJ Burnett are worth stars, but the rest of the Toronto rotation is very underrated.

Indians RAR/WAR in 2009

So, how do the Indians look in 2009? Will they need to add another starter?

The calculations for tERA and xIP are beyond my abilities at this point, so I cheated and used the innings pitched and ERA predictions from the 2009 Marcels. Here's what Marcel have to say for the guys currently on the 40 man roster.
Cliff Lee1803.80394
Fausto Carmona1354.13242
Zach Jackson834.7291
Aaron Laffey1124.26192
Jake Westbrook934.16162
Anthony Reyes844.45121
Scott Lewis724.00141
Jeremy Sowers1274.82131
Total Result88634.34147.0314.7

Uh oh. That 147.03 RAR would be, by 2008 standards, ninth best in the AL. But there are a few things to remember. Marcel is admittedly a "dumb" system, and it looks at three years of data. That means it's taking Cliff Lee's disappointing 2007 and Fausto Carmona's nightmare 2006 into account. Also, RAR is dependent on innings pitched. So, once the Indians settle on their five best starters, and give them the innings that went to "experiments" last year, the numbers should improve.