Zone Rating

看板Sabermetrics作者leddy (耿秋)時間18年前 (2007/05/13 11:56)推噓0(0推 0噓 0→)

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※ [本文轉錄自 NY-Yankees 看板] 作者: leddy (耿秋) 看板: NY-Yankees 標題: [統計]What is Zone Rating? 時間: Sun May 13 09:05:08 2007 因之前查Bobby Abreu的資料, 順道查到這篇好文Hardball Times的好文來源http://www.hardballtimes.com/main/article/what-is-zone-rating/ What is Zone Rating? by Sean Smith April 02, 2007 Zone rating has been around for 20 years now as a way to measure defensive players. It’s a simple concept; you just need to know two things: How many plays a fielder makes, and how many were hit into his zone. You divide the first number by the second, and you have zone rating. You can look at how many plays were made compared to an average fielder to get a plus minus rating, and that can easily be converted to runs to help us measure the overall worth of a ballplayer. There’s More than one Zone Rating? Last winter John Dewan and Baseball Info Solutions published The Fielding Bible and introduced a new version of zone rating. Dewan happens to be the guy who came up with the old Zone Rating when he worked for STATS, and he was able to add an improvement in the treatment of plays fielded outside of the zone. In the original Zone Rating, if a ball is hit outside of your zone but you range far enough to make a play anyway, that ball is added to both your plays made and your chances. The effect of this is to underrate players with outstanding range. Here’s an illustration: Take two shortstops, call them Billy and Jason. Both players have three ground balls hit near them, two in the shortstop zone and one just beyond it, hit straight up the middle. Jason makes plays on the two hit in his zone but cannot reach the other ball. Billy makes one play in his zone, makes an error on the other, but makes a great play on the ball hit up the middle. The zone rating for Jason is a perfect 2/2. For Billy, its 2/3, even though both players have had the same opportunities, and recorded the same number of outs. The new Zone rating treats these plays differently. Balls in zone counts only those hit into your zone, and there is a separate category for balls fielded outside your zone. Let’s Check the 2006 Results: The new Zone Rating is now available on The Hardball Times website. THT has data for the 2004 to 2006 seasons, and will add 2007 data as soon as the games begin. To get a feel for how the new feature, balls out of zone, affects a player’s rating, let’s take a look at the shortstops for 2006, using the new data but calculated the same way as the old Zone Rating: Name BIZ Plays ZR OOZ Chance Total Plays Above Plays AVG A. Everett 396 353 0.891 60 456 413 28 O. Vizquel 352 306 0.869 36 388 342 14 J. Reyes 359 308 0.858 40 399 348 11 C. Barmes 315 269 0.854 51 366 320 11 J. Bartlett 293 253 0.863 26 319 279 10 A. Gonzalez 269 230 0.855 42 311 272 9 E. Renteria 368 309 0.840 55 423 364 7 D. Eckstein 320 269 0.841 43 363 312 5 J. Uribe 333 280 0.841 40 373 320 5 K. Greene 286 238 0.832 36 322 274 2 R. Cedeno 322 265 0.823 54 376 319 1 J. Rollins 413 342 0.828 46 459 388 0 J. Wilson 401 330 0.823 48 449 378 -1 M. Young 458 375 0.819 53 511 428 -3 B. Hall 294 234 0.796 66 360 300 -4 C. Guillen 406 330 0.813 49 455 379 -5 R. Furcal 458 372 0.812 57 515 429 -6 Y. Betancourt 399 322 0.807 55 454 377 -6 M. Tejada 394 318 0.807 44 438 362 -8 D. Jeter 385 310 0.805 28 413 338 -11 H. Ramirez 368 290 0.788 61 429 351 -11 A. Berroa 364 286 0.786 36 400 322 -16 J. Peralta 459 364 0.793 46 505 410 -16 O. Cabrera 351 273 0.778 44 395 317 -17 Definitions: BIZ: Balls in zone Plays: Plays made in zone ZR: Zone rating OOZ: Plays made out of zone Chances: BIZ + OOZ Total Plays: Plays + OOZ Plays above average is found by finding the league average ZR, multiplying by Chances, and comparing to total plays made. This is for illustration purposes; I am using the total of this group of qualified players instead of the actual league average which would include starters and reserves. In addition, Chris Dial uses (correctly in my opinion) the AL and NL averages instead of an overall MLB average. There are factors (such as pitcher hitting) that make within league comparisons more accurate than overall comparisons. Now, let's try this again, treating balls outside of zone separately, so that we correctly reward both reliable fielders in their zone and players who make more plays outside of their zone. I will find the league average using only BIZ and Plays, and then do a separate calculation for balls outside of zone: Plays Above Name AVG Reliability Range New Total A. Everett 28 26 10 36 O. Vizquel 14 16 -9 7 J. Reyes 11 12 -6 6 C. Barmes 11 9 11 20 J. Bartlett 10 11 -11 0 A. Gonzalez 9 8 8 16 E. Renteria 7 6 8 14 D. Eckstein 5 5 2 7 J. Uribe 5 5 -2 3 K. Greene 2 2 0 2 R. Cedeno 1 -1 13 12 J. Rollins 0 1 -7 -5 J. Wilson -1 -1 -3 -4 M. Young -3 -3 -5 -8 B. Hall -4 -8 29 20 C. Guillen -5 -5 -3 -7 R. Furcal -6 -6 -1 -7 Y. Betancourt -6 -7 4 -3 M. Tejada -8 -7 -6 -13 D. Jeter -11 -7 -21 -29 H. Ramirez -11 -13 14 1 A. Berroa -16 -14 -10 -25 J. Peralta -16 -14 -12 -27 O. Cabrera -17 -16 -1 -17 We can compare the player’s OOZ plays to the average OOZ plays based on how many balls were hit in their zone. This is similar to what David Gassko and Chris Constancio did for defensive ratings in the Hardball Times Season Preview. For this to work we have to assume that the number of out-of-zone opportunities for players are proportional to their in zone opportunities. This may or may not be a good assumption. An alternative would be to use total ground balls as the denominator. A better way would be to create a measure of out of zone opportunities. For a shortstop we could take every groundball hit to the left of the third baseman or to the right of the second baseman, and subtract the ones already counted in the SS zone. This measure is not available, so for now I think using BIZ as an estimate is acceptable. “Reliability” is a measure using only balls in zone. For this group of shortstops, the average Zone Rating was .825. This group also made .1274 plays out of zone for every ball hit into the zone. “Range” compares the player’s out of zone plays made to this average, and the new total is simply Range + Reliability. The Highlights: Jason Bartlett did very well in Zone Rating but made very few plays outside his zone. In the end, he’s just an average shortstop. Bill Hall at the first step look a little below average, but made a tremendous number of plays outside his zone. This year he is being moved from shortstop to center field, but this may be a mistake as he makes many more plays than the average shortstop. Derek Jeter looks a little below average at first, but he’s even worse than that. Jeter has very limited range. Only Bartlett made fewer plays outside the zone, but Jeter played almost 50% more innings than Bartlett. Hanley Ramirez looks below average at first, tied with Jeter, but made a great number of plays out of his zone. He’s actually average or slightly above. Adam Everett already ranked far above any other shortstop in the game, but in addition to fielding everything hit near him he has excellent range as well. He may be the best defensive shortstop since Ozzie Smith. -- ※ 發信站: 批踢踢實業坊(ptt.cc) ◆ From: 220.132.198.21 -- ※ 發信站: 批踢踢實業坊(ptt.cc) ◆ From: 220.132.198.21