本研究主要探討兩個提升球隊投手戰力的方式，其一為外部補強，透過自由球員簽約引進即戰力；其二則是內部強化，透過分析投手面對不同慣用手打者的優劣勢，找出能夠讓投手具有優勢的投球策略，來提升投手的戰力。

2021年11月，投手Max Scherzer與紐約大都會隊簽下年均薪4333萬美元的合約，打破大聯盟球員年均薪紀錄。2019年12月，投手Gerrit Cole與紐約洋基隊簽下合約總值3.24億美元的合約，創下大聯盟投手合約總值最高紀錄。當大聯盟球隊開始花費大量預算，透過簽下自由球員投手來補強球隊，就要考量簽下自由球員所要承擔的風險，例如球員在合約年表現比以往出色的合約年現象，以及簽約後成績衰退的怠惰現象。因此，本研究專注於自由球員投手的合約年和怠惰現象研究，並透過機器學習模型來預測投手是否會發生怠惰行為。最終結果發現，投手沒有合約年現象，但是有出現怠惰現象，並且投手的成績數據相較於投手的個人背景資料，更能有效預測投手是否會發生怠惰現象。

球隊要增強投手的戰力，並不限於簽下自由球員補強，隊內的投手若是能夠制定合適的投球策略來改善投球成績，也能夠讓球隊戰績提升。本研究從「左投剋左打」這句廣為流傳的棒球名言切入，檢驗左投對左打、左投對右打、右投對右打與右投對左打四種投打慣用手組合之中，投手投到哪一個進壘位置以及使用哪一個球種，能夠最有機會解決打者。此外，若將打者型態分為長打型打者與非長打型打者，檢驗在四種投打慣用手組合中，結果是否與不分打者型態相同。最終本研究發現，投手只要將球投到外角低與好球帶上緣高的進壘位置，與其他位置相比，對於投手而言都是較佳的選擇，唯一的例外是投手為左投且面對非長打型的左打者。

This thesis aims to study the two ways to improve the pitchers’ ability in a baseball team. One is the signing of free agents, and the other is strengthening the pitchers in the team by finding an advantage when facing an opposite handedness batter.

In November 2021, Max Scherzer signed a $43.33 million annual wage contract with the New York Mets, breaking the major league record for average annual value, and in December 2019, Gerrit Cole signed a $324 million contract with the New York Yankees, breaking the record for the highest contract value for a major league pitcher. As major league teams begin to spend large budgets to strengthen their teams by signing free agent pitchers, it is important to consider the risks associated with signing free agents, such as the contract year phenomenon where players perform better than ever before in the contract year, and the shrinking phenomenon where performance declines after signing the contract. Therefore, this study focuses on the contract year and the shrinking phenomenon of free agent pitchers and uses machine learning models to predict whether shrinking will occur in pitchers. The results revealed that there was no contract year phenomenon, but there was shrinking, and the performance of the pitcher was more effective in predicting whether shrinking would occur compared to the pitcher's personal background information.

If teams want to strengthen their pitchers, it is not limited to signing free agents, but can also be improved if the pitchers can develop appropriate pitching strategies to improve their performance. In this study, we examined four handedness combinations between pitcher and hitter. The purpose of this study was to investigate which location and pitch type would give a pitcher a better chance to retire a hitter. In addition, if the batter were divided into slugger and non-slugger hitters, the results were tested to see if the results were the same without dividing the batter. In the end, the results revealed that the pitcher who threw the ball to the low outside corner and a high upper edge of the strike zone was a better choice for the pitcher than the other positions in the zone, with the only exception of the pitcher who was a lefty and faced a non- slugger lefty hitter.

論文審定書 i
摘要 ii
Abstract iii
目錄 v
圖目錄 vi
表目錄 vii

第一章 緒論 1
第一節 研究動機與目的 1
第二節 研究問題與架構 4

第二章 文獻探討 5
第一節 大聯盟的自由球員制度 5
第二節 合約年與怠惰現象 7
第三節 均值迴歸 9
第四節 相異慣用手之投球策略 11

第三章 研究方法 12
第一節 資料來源與篩選－合約年與怠惰現象研究 12
第二節 資料欄位介紹－合約年與怠惰現象研究 13
第三節 研究流程－合約年與怠惰現象研究 17
第四節 資料來源與篩選－相異慣用手之投球策略分析 19
第五節 資料欄位介紹－相異慣用手之投球策略分析 19
第六節 研究流程－相異慣用手之投球策略分析 21

第四章 研究結果 23
第一節 合約年與怠惰現象研究 23
第二節 相異慣用手之投球策略分析 33

第五章 結論與建議 47
第一節 研究結論－合約年與怠惰現象研究 47
第二節 研究限制與建議－合約年與怠惰現象研究 49
第三節 研究結論－相異慣用手之投球策略分析 50
第四節 研究限制與建議－相異慣用手之投球策略分析 52

參考文獻 53

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