Re: [情報] WAR, a case study: Fielder vs. Ryan

[gn02530640 (憂)]

我英文很差，尤其第四段 WAR 的解釋我不確定翻得對不對，
希望版友們能多提供我一些建言(請盡量鞭用力一點 XD)，感謝:)

※ 引述《abc12812 ()》之銘言：
: http://tinyurl.com/czyedbm
: The other night I tweeted that Prince Fielder's 50-homer season in 2007 --
: when he hit .288/.395/.618 -- rates as the lowest wins above replacement
: total among the 42 seasons a player has hit at least 50. His 3.4 WAR on
: Baseball-Reference is one of just three of those 42 seasons the site
: evaluates as worth fewer than 5.0 wins, Mark McGwire's 4.9 in 1997 and Sammy
: Sosa's 4.5 in 1999 being the other two.

Prince Fielder 在07年敲了50轟，繳出 .288/.395/.618 的優異打擊三圍。
在MLB歷史上一共有42個球季曾出現過達成單季50轟成就的球員，
而 Fielder 2007年的 WAR 卻僅僅只有3.4勝，是所有達成50轟的球員中最低的。
依照Baseball-Reference的WAR統計，只有三位達成50轟的球員他們那一年的WAR不到5，
分別是Fielder、1997年的 Mark McGwire(4.9)以及1999年的 Sammy Sosa(4.5)

: I followed up that factoid by mentioning that in 2012 Mariners shortstop
: Brendan Ryan -- who hit .194 with a .277 on-base percentage and three home
: runs -- was worth 3.3 WAR. How can two players of such extreme differences in
: offensive production be valued so similarly? As somebody mentioned in a
: follow-up tweet, it's numbers like this that make many fans skeptical of WAR
: … or completely dismissive.

Brendan Ryan 2012年的打擊率是1成94，上壘率2成77，而且只揮出3轟，
但他的 WAR 卻高達3.3勝。
為什麼在進攻端差異如此懸殊的兩人對球隊的貢獻卻幾乎是相等的？
這也是為什麼很多球迷對 WAR 這樣一個數據的正確性抱持懷疑的態度，
甚至根本不屑一顧。

: With that in mind, I thought it would be a good idea to do a rough example of
: how WAR is calculated, using Fielder and Ryan -- and why it does work and why
: it (hopefully) makes sense. (For a much more thorough description, here is
: the Baseball-Reference explanation page, including the idea behind WAR and
: the concept of replacement level, and here's the specific page on the steps
: used for rating position players.)

: As Sean Forman writes on Baseball-Reference, "The basic currency of WAR is
: runs. We start with runs added or lost versus an average player and then
: compare the average player to a replacement player." The formula is this:
:     Players Runs over Replacement = Player_runs - ReplPlayer_runs =
: (Player_runs - AvgPlayer_runs) + (AvgPlayer_runs - ReplPlayer_runs)
: OK, we'll start with runs on offense.

我認為 Fielder V.S. Ryan 正好是解釋 WAR 是如何計算的一個很棒的範本，
究竟 WAR 是怎麼得來的，以及為什麼(我誠摯地希望)它是有意義的。

(原文連結：
(1) Baseball-Reference 對 WAR 的解釋：
http://www.baseball-reference.com/about/war_explained.shtml)
(2) 對於野手的 WAR 計算及相關細節：
http://www.baseball-reference.com/about/war_explained_position.shtml)

如同 Sean Forman 在 Baseball-Reference 上所寫的：
「各家學派計算 WAR 的基本共通點就是"計算得分(runs)"。」
  (註：不是比賽的實際得分，比較像是在打分數)

  我們先將欲比較的球員和一位平均水準的球員做對照，並計算兩者之間的正負值，
  然後再比較一般平均水準的球員和替補等級的球員(replacement player)間的差距。

公式：Players Runs over Replacement = Player_runs - ReplPlayer_runs =
: (Player_runs - AvgPlayer_runs) + (AvgPlayer_runs - ReplPlayer_runs)

好了，以下就讓我們先從進攻上的得分開始談起。

: Offense
: Using the linear weights method of evaluating offense -- giving value to each
: single, double, triple, home run, walk, hit by pitch, sacrifice and even
: reached on error -- Fielder created 143 runs in 2007. Ryan created 35 runs,
: so Fielder is off to a 108-run advantage right off the bat.

: But remember that we have to factor in the context those runs were created
: in. The National League in 2007 hit .266/.334/.423 (and even higher when you
: filter out pitcher hitting) and the American League in 2012 hit
: .255/.320/.411, which means Fielder will be compared to a better average
: hitter than will Ryan. Fielder also played in Miller Park, which is rated as
: a neutral park for the three-year park factors Baseball-References uses (park
: factor of 100), while Ryan played in Safeco Field, an extreme pitchers' park
: (park factor of 90, decreasing run scoring by 10 percent). So Ryan played in
: a tougher offensive environment, which means his batting runs are accordingly
: adjusted.

: Also, playing time -- Fielder produced his runs in 681 plate appearances
: while Ryan had 470. When each hitter is then compared to what a
: league-average hitter would produce in that amount of playing time, Fielder
: ends up at plus-44 runs and Ryan at minus-18, so the difference on offense is
: now 62 runs.

進攻端：
在計算進攻上的得分採用加權法。對於每一支一壘安打、二壘打、三壘打、全壘打、
保送、觸身、犧牲打甚至是靠失誤上壘賦予不同的價值。

按照此公式可計算出 Fielder 2007年創造出的得分是143分，2012年的 Ryan 則是35分。
因此我們發現 Fielder 靠著他的大棒子比 Ryan 創造出多達108分的得分。

但除此之外我們還必須將當時的環境、背景等因素考慮進去。2007年國聯平均打擊三圍
是.266/.334/.423(尤其若扣除掉投手打擊的部分應該會更高)，而2012年美聯平均打擊
三圍是.255/.320/.411，這意謂著 Fielder 的比較標準應該要比  Ryan 來的高。而且
小王子當時是在 Miller Park (照 Baseball-References 的評估算是比較中立的球場)
打球，然而 Ryan 卻是待在 Safeco Field(極偏投手的球場)，因此 Ryan 的進攻得分
勢必得作調整。

此外還有上場時間 - Fielder 07年擁有681個打席，相對來說 Ryan 只有470個。接著
我們假設一個平均水準的球員擁有和 Fielder 及 Ryan 相同的打席，計算出該平均水
準的球員所創造出的得分，最後再和 Fielder 和 Ryan 做對照得到我們所要的結果。
小王子比一般平均水準球員多創造 +44 的得分，Ryan 則是-18。因此經過調整後兩人
在進攻上的得分實際差距大約是62分。

: Baserunning and runs on avoiding double plays
: It should not surprise you that a guy coming in somewhere close to 300 pounds
: doesn't earn extra value with his baserunning (including stolen bases and
: caught stealing). Fielder is minus-3 runs on baserunning, but plus-1 on
: double plays as he grounded into just nine that year. Ryan was average (zero
: runs) in both areas, so picks up two more runs in value, leaving Fielder at
: plus-60 runs.

跑壘(包含盜壘和盜壘失敗) & 避免被雙殺：
不意外，小王子在跑壘上的得分是 -3，不過避免被雙殺的部分則是+1(當年他只有9次
雙殺打)。Ryan 在兩方面則皆屬於平均水準(得分都是0)，因此 Ryan 在這一塊比小王
子多出+2分，現在兩人得分上的差距縮小至60分。

: Defense
: This is the aspect of the game where Ryan shines. Baseball-Reference uses
: defense runs saved from Baseball Info Solutions, which evaluates every batted
: ball in a variety of categories, and then compares each player to the average
: fielder at his position. Ryan is rated at plus-27 runs, a very high figure --
: the second highest of any fielder in 2012, and the fifth highest by a
: shortstop in the past decade.

: Fielder, meanwhile, is rated at 15 runs worse than an average first baseman,
: a very poor total.

防守端：
Ryan 在守備方面可說是大放異彩。Baseball-Reference 在防守上採用的是 Baseball
Info Solutions 的 "defense runs saved" 來做評估，將"每一位野手"和"該野手所負責
的守位的平均水準"作比較。計算後 Ryan 得到了+27分，是2012年第二高分，也是近十年
游擊手得分第五名；而 Fielder 比起平均水準的一壘手是-15分，相當差的數字。

: Look, are defensive stats perfect? No. Are they pretty good these days? Yes.
: Should one-year defensive stats in particular be viewed with some
: reservations? Sure. Was Ryan's 2012 season a defensive fluke? I don't think
: so. Defense runs saved has him at plus-25, plus-22, plus-18 and plus-27 in
: his four seasons as a regular, the first two with St. Louis, so it has
: consistently given high marks to his glove work.

但，守備數據是完美的嗎？顯然不是。
然而守備數據雖然不是完美的，但也已經很不錯了。

所以特地拿 Ryan 在2012年的守備表現來計算而得到這樣的結論，是不是應該要對此
結果持保留態度呢？ 是的。

所以 Ryan 的2012在防守上的好表現會不會只是僥倖賽到的？抱歉我不這麼認為。
Defense runs saved 計算 Ryan 過去4年的守備得分分別是+25、+22、+18和+27，
前兩個數字是他還待在紅雀時的守備得分。因此我們可以從這裡看出 Ryan 的守備表現
是相當穩定的。

: As for Fielder, everyone would agree that he's not exactly Keith Hernandez at
: first base. He's a big, heavy guy without much quickness who also made 14
: errors that year. It's certainly plausible that he was 15 runs below an
: average first baseman (his defense has rated better in recent seasons).
: So Ryan has a huge 42-run advantage on defense, leaving Fielder at plus-18
: runs.

關於小王子，所有人都應該會同意他並不是 Keith Hernandez。他不僅體格龐大、又胖
、反應又遲緩，當年他也發生14次失誤。所以對於"小王子比起守備平均水準的一壘手
要少了15分"這一結論我認為是可以相信的(不過小王子這幾年守備有比較好了)。所以
Ryan在防守上比小王子多得到+42分，現在小王子的領先數字從+60分大幅縮減至+18分。

: There are those who will argue that the value of defense is being overrated,
: that the margins between the best and worst fielders can't be that high.
: Well, why not? Ryan had 601 total chances in the field in 2012 -- about a
: full season's worth of plate appearances for a hitter. Sure, many of those
: are routine grounders and easy pop-ups that any competent major league
: shortstop can field. But a certain percentage of possible plays are not
: routine, and that's where defensive value comes in to play. As for Fielder,
: he made 423 outs at the plate in 2007, so he's not obtaining any value in
: about two-thirds of his plate appearances, as well.

可能會有人說守備價值被過分高估了，即使手套最好和最差的防守球員間也不應該會有
如此龐大的差距。但，為什麼你認為不會有呢？Ryan 在2012年一共有601次的守備機會
，價值跟一個打滿整季的打者的打席數是相同的。喔好啦，這601次守備機會當中確實
有很多次只是非常簡單的的滾地球和可以輕鬆接殺的內野飛球，但不好處理的play也佔
了一定的比重，而能夠完成這些困難的play正是守備的價值所在。以 Fielder 來說，
2007年他在打擊上同樣製造了423次出局，因此他的681次打席其實有佔將近2/3是沒有
辦法創造出任何貢獻的，這道理就跟守備是一樣的。

: Final adjustments and wins
: The final adjustment made is a positional adjustment. Obviously, it requires
: more ability to play shortstop than first base, as reflected by the fact
: teams will play lesser hitters there. Since Ryan was being compared only to
: other good fielders at his position, and Fielder only to other first basemen,
: that has to be factored in. Baseball-Reference's current values for
: positional adjustment are plus-7.5 runs for shortstops (per 1,350 innings
: played) and minus-10 for first basemen. This ends up giving Ryan plus-6 runs
: and Fielder minus-10.

: Which puts us at … Fielder at plus-2 runs.

最後是關於守備位置的調整。而且很顯然地，想當一個游擊手比當一壘手要更困難，
這從各球隊的守備位置人數分布多寡就可以看得出來。因此 Ryan 只能跟其他手套
同樣很優的球員來比較，而小王子也只需要和其他守備相對於游擊手來說比較不佳的
一壘手作比較。

Baseball-Reference 目前對於游擊手的調整分數是 +7.5/每守備1350局，而一壘手
則是 -10，結算 Ryan 得到+6分，Fielder 則是-10分。

所以在經過計算後 Fielder 最終只比 Ryan 多了2分。

: From there, runs are converted to wins, and Fielder ends up at 3.4 wins above
: replacement and Ryan at 3.3. It's important to keep in mind that WAR is an
: approximation of value, not a definitive answer, but I hope this helps in
: explaining why a player who hit .194 can be viewed with the same value as a
: player who hit 50 home runs.

: By the way, Fielder's WAR in 2012: 4.4. Even though he hit only 30 home runs.

最後我們再將得分轉換成對球隊勝負的貢獻，得到 Fielder 比起 replacement player
要多貢獻了3.4勝，Ryan 則是3.3勝。但我們必須要切記的是，WAR 只是一個近似值，而
不是絕對的答案。但是我希望這能夠有助於解釋，為何一個打擊率才1成94的球員和一個
能幹出50本的球員是具有同等價值的。

順帶一提，Fielder 2012年只敲了30轟，但他的 WAR 卻是4.4。

(完)

--
※ 發信站: 批踢踢實業坊(ptt.cc)
◆ From: 36.231.53.243
推 nickyang:主詞是守備數據
→ nickyang:守備數據不完美但已經很不錯了
→ gn02530640:感謝樓上!
推 daniel955377:Are they pretty good these days?的they應該是
→ daniel955377:defensive stats吧?
→ gn02530640:我一看到"they"第一直覺就覺得是指人 XD 現在回過頭
→ gn02530640:看主詞其實很明顯就是指前一句的守備數據 囧rz
推 Guillen:推，我覺得翻得很好啊，原po謙虛了 XD
推 Seiran:推  原PO優秀!
→ pujos:我對最後那一段的Rpos修正有疑問
→ pujos:在進攻端的評估已經對pos做過一次修正.沒理由最後還要在一次
→ pujos:光看這兩季米高的WAR就很清楚了
→ gn02530640:進攻方面沒有做守位校正吧@@
→ pujos:最後的Rpos校正直接影響他在BR版的WAR有1的差距
推 NickWeglarz:進攻哪裡有對守位做過校正？
推 nickyang:2012五月之後BR板的有
→ NickWeglarz:WAR架構的重點就是把攻守分開，不再像VORP一樣拿進攻
→ pujos:打錯是Rfield...
→ NickWeglarz:數據作防守校正
→ pujos:單就相同位子的球員來比WAR.那有相當程度的可信度
→ pujos:不過一但跨位子.可能這也不是個好的比較選項
推 porten812:推
※ 編輯: gn02530640      來自: 36.231.53.243        (03/01 13:35)
推 god2:推
推 Lasvegas:PUSH~
推 Yginger1:推 感謝
推 ajburnett:現在都流行先消毒嗎？ lol
推 vg175:推用心翻譯
推 niravaabhas:推!感謝 不過Miller park我覺得很偏打者耶...
推 maxspeed150:PF 104 中性略偏打者而已
→ maxspeed150:Chase 106, Coors 120, Great American 107都比較高
推 miabcd199:推翻譯
推 andy880036s:
推 AStigma:好文＋原PO用心，感謝！
→ uranusjr:Miller Park 會讓人覺得偏打者是 Fielder 和 Braun 造成
→ uranusjr:的錯覺吧, 感覺好像很容易打XD
推 dw1012:最近讓我覺得Miller Park是打者球場都是因為青木宣親!!
推 WarlockRudy:用心的好文章，推!!! 長知識!
推 bravefan:感謝翻譯，讓懶得看或看不懂的大家都能讀到這篇好文~^^