## 2006 NRAA: Tweaks and Updates

As promised, I made some changes to Net Runs Above Average, with some help from Richard Wade and David Gassko. First off, let's start by recapping what it is that Net Runs Above Average does, for two reasons. The first being to introduce those who may not be familiar with it to the statistic itself. Secondly, it has been around for almost a year and I still haven't written a single definitive article for it.

Net Runs Above Average is meant to show offensive and defensive above average run value in one tidy number for easy analysis and inspection. It has rate forms and a cumulative form, and it is also easily adjusted to whatever you want to see with some simple arithmetic. Originally -- well, not originally, but within the last inception of it -- the components were primarily Equivalent Average and Rate2, both Baseball Prospectus statistics. EqA was an easy choice, as it is one of my favorite offensive statistics, and updated daily. Fans of Base Runs might take issue with that, and I am open to suggestion as always -- I try not to get too attached to any of this in the event that something better comes along.

Which brings me to my next point: we have converted over from Rate to Zone Rating, at the behest of more people than I expected. I had been thinking about converting over to something else, but I was not sure what exactly. After writing a the team previews this offseason, and seeing how many inconsistencies there were in Rate in comparison to other fielding systems out there, I decided that I might as well go through with it. Zone Rating seems to make the most sense, as it correlates well with some of the more accurate fielding systems out there, and is also available just as easily as Rate.

As far as the actual inputs into NRAA go, there is some explaining that needs to be done I think. To calculate the offensive runs above average, we use this formula (EQRAA is equivalent runs above average):

EQRAA = (5*OUTS*EqA^2.5)-(5*OUTS*.26^2.5)

The .260 might need some explanation. That is league average EqA for all batters. To calculate the defensive runs above average, we now tweak Zone Rating into something that Richard called "ZRate" (still listed as ZR in the table for space purposes). This is figured by calculating the chances and plays above average for a fielder at a given position, and then using Chris Dial's run value for an out for each position times the plays above average to figure the ZRate, or runs above average for that player. This number is then plugged into the spreadsheet where Rate used to be, and NRAA is born once all the fields are filled out properly.

Formerly, NRAA was normally in a per 100 game form, due to the use of Rate, which is also in that form. I was convinced about 15 minutes before writing this that converting to 150 games would make more sense, as it is a full season. I've switched over for now, and we'll see how it goes from there. Besides that, the only changes were in fitting the spreadsheet over to ZR rather than Rate.

The other version of NRAA that you will actually see more often is positionally adjusted Net Runs Above Average. NRAA is the raw form; pNRAA is the more accurate reflection of above average run value, due to its additional adjustments. The only real changes to pNRAA come in the equation for EQRAA:

pEQRAA =(5*OUTS*EqA^2.5)-(5*OUTS*pEqA^2.5)

pEqA replaces the .260, and that figure is whatever the average EqA for the position we are calculating is. This is possible now that BP has started to list the EqA's by position in their statistics reports, which makes my job a great deal simpler.

I have included a table in this article that lists the top 40 centerfielders according to pNRAA as of May 15. I am also including a spreadsheet attachment with the same numbers for sorting purposes, so people can play with it if they want to, as well as the ZRate sheet for center. I figure that this will be one of the easiest ways to get feedback and criticisms out there, since they most likely do a better job explaining the process than I can.

Centerfield NRAA & pNRAA thru 5-15-06
 Player OUT EQA G EQRAA ZR pEQRAA pEqA NRAA NRAA/G NRAA/GP pNRAA pNRAA/GP Carlos Beltran 72 .333 27 10.63 2.84 10.75 .259 61.88 .413 11.14 62.54 11.26 Vernon Wells 99 .326 36 12.97 3.22 13.14 .259 57.28 .382 13.75 57.96 13.91 Ryan Church 42 .323 20 5.21 -1.12 5.28 .259 37.98 .253 5.06 38.5 5.13 Jason Repko 50 .315 24 5.31 0.64 5.39 .259 33.8 .225 5.41 34.31 5.49 Andruw Jones 101 .303 37 8.11 0.26 8.28 .259 33.15 .221 8.18 33.83 8.35 Torii Hunter 119 .290 38 6.44 1.34 6.63 .259 26.75 .178 6.78 27.53 6.97 Grady Sizemore 119 .290 38 6.44 -0.24 6.63 .259 25.17 .168 6.38 25.95 6.57 Wily Mo Pena 60 .296 27 3.96 1.88 4.06 .259 23.88 .159 4.3 24.43 4.4 Steve Finley 71 .300 32 5.26 -1.53 5.38 .259 23.14 .154 4.94 23.69 5.05 Gary Matthews Jr. 77 .288 26 3.87 -3.59 3.99 .259 18.72 .125 3.24 19.45 3.37 Randy Winn 111 .277 38 3.28 2.56 3.47 .259 15.52 .103 3.93 16.24 4.11 Jim Edmonds 86 .282 33 3.34 -0.51 3.48 .259 14.66 .098 3.22 15.3 3.37 Eric Byrnes 67 .284 29 2.85 -0.2 2.96 .259 14.55 .097 2.81 15.12 2.92 Shane Costa 42 .286 18 1.95 -1.74 2.02 .259 14.49 .097 1.74 15.07 1.81 Aaron Rowand 90 .282 32 3.49 -2.81 3.64 .259 13.56 .090 2.89 14.26 3.04 Johnny Damon 110 .275 36 2.85 1.14 3.04 .259 13.03 .087 3.13 13.79 3.31 Endy Chavez 46 .272 23 0.95 3.66 1.02 .259 9.83 .066 1.51 10.33 1.58 Kenny Lofton 74 .269 25 1.13 2.02 1.25 .259 8.82 .059 1.47 9.55 1.59 Curtis Granderson 104 .267 36 1.23 0.9 1.4 .259 6.03 .040 1.45 6.74 1.62 Cory Sullivan 107 .266 35 1.08 1.19 1.26 .259 5.83 .039 1.36 6.59 1.54 Corey Patterson 65 .266 26 0.66 1.8 0.76 .259 5.59 .037 0.97 6.21 1.08 Willie Bloomquist 34 .270 18 0.58 0.02 0.64 .259 4.85 .032 0.58 5.32 0.64 Marlon Byrd 66 .270 29 1.13 -1.71 1.23 .259 4.11 .027 0.79 4.68 0.9 Ken Griffey Jr. 37 .265 12 0.31 -0.01 0.37 .259 3.88 .026 0.31 4.64 0.37 Jeff DaVanon 57 .265 28 0.48 0.52 0.57 .259 3.09 .021 0.58 3.59 0.67 Mike Cameron 62 .257 20 -0.31 3.86 -0.2 .259 1.57 .010 0.21 2.34 0.31 Mark Kotsay 101 .244 34 -2.56 -1.17 -2.39 .259 -12.45 -.083 -2.82 -11.71 -2.65 Ryan Freel 91 .238 33 -3.11 -0.14 -2.96 .259 -14.28 -.095 -3.14 -13.59 -2.99 Reggie Abercrombie 78 .230 27 -3.55 1.28 -3.42 .259 -18.44 -.123 -3.32 -17.72 -3.19 Nathan McLouth 61 .221 31 -3.51 -1.64 -3.41 .259 -18.62 -.124 -3.85 -18.14 -3.75 Willy Taveras 120 .230 38 -5.46 0.33 -5.26 .259 -21.22 -.141 -5.38 -20.44 -5.18 Joey Gathright 88 .216 35 -5.63 1.88 -5.48 .259 -22.23 -.148 -5.19 -21.61 -5.04 Brady Clark 97 .224 36 -5.2 -0.61 -5.04 .259 -22.28 -.149 -5.35 -21.61 -5.19 Darin Erstad 63 .215 21 -4.11 2.7 -4 .259 -26.63 -.178 -3.73 -25.89 -3.62 Brian N. Anderson 79 .208 29 -5.82 0.69 -5.69 .259 -29.42 -.196 -5.69 -28.75 -5.56 Juan Pierre 122 .210 37 -8.7 4.96 -8.5 .259 -30.31 -.202 -7.48 -29.49 -7.27 Jeremy Reed 73 .210 27 -5.2 -2.42 -5.08 .259 -31.34 -.209 -5.64 -30.67 -5.52 Eric Reed 34 .127 21 -4.88 0.2 -4.83 .259 -34.68 -.231 -4.85 -34.27 -4.8 Kerry Robinson 42 .218 13 -2.58 -5.33 -2.51 .259 -35.09 -.234 -3.04 -34.29 -2.97 Chris Duffy 79 .187 29 -7.64 -1.6 -7.51 .259 -41.13 -.274 -7.95 -40.45 -7.82

Considering these are early season statistics, I don't want to put too much stock or commentary into them. But as someone who has been watching Wily Mo Pena play in the outfield, I think that he might be getting a little too much love defensively. And Shane Costa comes in 14th overall among centerfielders, while teammate Kerry Robinson comes in at 39th. And it looks as if Vernon Wells really is as good as the ESPN crowd expected him to be this year. If he keeps it up, kudos to whoever had the fortitude to run that MVP article on the front page. If not, no big deal, Wells will most likely remain an improvement over the past two years. And hey, Endy Chavez isn't half bad so far this year. I feel like I need a shower after saying that, but still, he's holding his own, and good for him. But this just in, Darin Erstad still sucks. There, I feel better.

## Trending Discussions

forgot?

As part of the new SB Nation launch, prior users will need to choose a permanent username, along with a new password.

I already have a Vox Media account!

### Verify Vox Media account

As part of the new SB Nation launch, prior MT authors will need to choose a new username and password.

We'll email you a reset link.

Try another email?

### Almost done,

By becoming a registered user, you are also agreeing to our Terms and confirming that you have read our Privacy Policy.

### Join Beyond the Box Score

You must be a member of Beyond the Box Score to participate.

We have our own Community Guidelines at Beyond the Box Score. You should read them.

### Join Beyond the Box Score

You must be a member of Beyond the Box Score to participate.

We have our own Community Guidelines at Beyond the Box Score. You should read them.