The previous resource review was about a book that revealed connections of mathematics (especially probability) to baseball. I can hear you asking...there must be others...?
A lot of resource texts are available, primarily in the areas of probability and statistics. Any of the following will be a good start...
Alan Schwarz' book The Numbers Game: Baseball's Lifelong Fascination with Statistics provides a historical perspective of the close connections of statistics to baseball since its very beginning.
In contrast, Eranshaw Cook's Percentage Baseball uses mathematics to impact the playing of baseball, ranging from the benefits of a sacrafice bunt, the use of relief pitchers, the impact of differing batting orders, the hit and run play, and even pitching strategies.
Michael Schell's book Baseball's All-Time Best Hitters: How Statistics Can Level the Playing Field argues that Tony Gwynn is the greatest hitter of all time, when raw batting average is adjusted by factors such as era, rule changes, and changing ballparks.
Co-authored with Jay Bennett, Jim Albert's book Curve Ball: Baseball, Statistics, and the Role of Chance in the Game provides a quite rigorous look at how statistics can impact how baseball is both understood and played.
And Jim Albert's other book Teaching Statistics With Baseball does exactly what it claims to do....
Hope you find these books helpful. If you know of others, please let me know so that I can add them to this list.