Years with Boston: 1907-1915 (.337/.414/.482, 39 home runs, 542 RBIs, 267 stolen bases)
Best Year in Boston: 1912 MVP (.383/.464/.567, 10 home runs, 90 RBIs, 53 doubles, 52 stolen base)
Speaker was a part of two World Series Champion clubs in 1912 and 1915. 1912 was his best season with the Red Sox and he was named the MVP that year, given the Chalmers Award, which was the name of the award at the time. Speaker lead the league in doubles and home runs that season. His success that season carried over into the World Series. In 1915, Speaker was not able to hit a single home run, nevertheless he hit .322/.416/.411 and still had a terrific year.
Speaker was a phenomenal hitter for Boston, but his defense also drew some attention. Speaker played very shallow in center field and was able to cut down base hits and throw out runners. He was almost an extra infielder.
Unfortunately, due to a contract dispute, Boston ended up trading Speaker before the 1916 season for Sad Sam Jones and Fred Thomas. He continued to play very well, possibly even better for Cleveland. Speaker's time in Boston was very important to his Hall of Fame case and likely would not have been in the Hall without it, but he was even more successful in Cleveland.