Publication:

職棒球員生涯表現分析

職業球團與球員簽訂合約的年數與年薪，以及球員交易，都需要預測球員未來的表現。目前職業球團普遍使用的方法，就是根據該球員前幾年的表現，因此需要明確的評估方法，可以用來預測球員未來的表現。本研究之目的為根據四項修正後的數據: 三壘安打率、打擊率、保送率、純長打率，探討美國職棒與中華職棒打者生涯表現的趨勢。研究對象為美國職棒1987-2006年共20個球季間，至少出賽8年以上，且每年都出賽達到regular player 標準的打者，共有223名球員，以及中華職棒方面1990-2007年間，生涯打席數超過1000以上的打者，共有147名球員。為了將不同年代的球員表現都放在同一個基準點上比較，美國職棒部份，根據Schell (2005) 所使用的各個數據修正方式，將各球員各年的數據轉換成以1977-1992年國家聯盟為基準，中華職棒則以每一項成績與當時的聯盟平均水準做比較，得到相對於聯盟平均水準的成績。之後再將轉換後的數據對年齡繪製趨勢圖，分析球員生涯變化趨勢。結果發現，在美國職棒以速度見長的選手，在27歲左右達到生涯的巔峰，之後便逐漸下降；打擊率方面，高打擊率的選手，通常附帶著一定的選球能力和長打率，而生涯表現也相對的穩定；選球方面，隨著年齡增長，呈現日漸上升的趨勢，因此可知，隨著經驗累積，有助於提升選手被保送的能力；長打雖會隨年齡增長而衰退，但是幅度並不大，因此，生涯純長打率在聯盟前25%的球員，即便已超過30歲，都還有一定的長打威力。中華職棒也呈現出類似的現象，只是球員生涯的巔峰出現較早，可能是受到兩國職棒制度的差異所造成。透過本研究，可提供球團在簽訂球員合約，以及進行球員交易時的參考。

The prediction of performance for professional baseball players is required in determining the length and price of contracts and trades. The Method which teams generally use at present, is according to this player's performance in previous years. Therefore, a more reliable method is required to estimate the future performance of the players. The purpose of this research is to analyze the trend of career performance in Major League Baseball and Chinese Professional Baseball League using 4 adjusted statistics: triple rate, batting average, base on balls, and isolated power. The subjects included Major League Baseball players who have played regularly at least 8 years during 1987-2006, totaling 223 players. The players who have had 1000 or more career at bats during 1990-2007 in Chinese Professional Baseball League were also involved, totaling 147 players. In order to compare the players from different era, statistics from Major League Baseball was converted to the standard of National League during 1977-1992, according to Schell (2005). The statistics in Chinese Professional Baseball League was compared to the league average of the year. The converted data was used to analyze the performance change throughout the career. The results showed that, in Major League Baseball, the players with good speed reached their peak in about 27 years old, then showed steady decline. The players with high batting average usually combined with good baseball on ball ratio and slugging average. The performance of these players was relatively stable throughout the career. The ability to get base on balls increased with age, indicating that the experience can help. Slugging average showed small magnitude of decline with age. The players with career isolated power in top 25% of the league still maintained considerable slugging power after 30 years of age. The results were similar in Chinese Professional Baseball League, but the peak performance in the career was reached in the earlier age then that in Major League Baseball. The results of this study can be used as the reference for signing contracts and trading players.

For is it given to same datum point is it compare to pay to display player of various years, and probe into different ability separately, this research is adopted by Schell (2005) All data used revise the way, calculate player's data through 5 steps, drawing the trend picture to the age after changing, find out player's career development trend, for using to assess player's ability.

Found finally, an excellent player good at the speed of MLB about 27 years old to reach the peak of the career, later dropped gradually. The player of the high batting average, usually lead attaching certain on base ability and power, and career performance relative stability too. The base on balls ability increase with the age, the trend of rising day by day appears. Although player's power will decline with the age, the range is not big, so, player's career pure power rate at the top 25% in the league , even if already over 30 years old, have certain hold their power. The CPBL have similar phenomenon too. The only different is the peak of player's career performance is earlier than MLB. It may due to the difference of professional baseball system in different countries.