Top 10 most impactful MLB trade deadline moves of all time

6. Jake Peavy, Boston Red Sox (2013) and San Francisco Giants (2014)

Peavy played a key role in not one, but two different World Series title runs in back-to-back seasons. In 2013, Peavy started the year 8-4 with a 4.28 ERA in 13 starts as a member of the Chicago White Sox before being traded to Boston. With the Red Sox, Peavy went 4-1 with a 4.04 ERA in 10 starts. While his postseason stats with a 0-1 record and 7.38 ERA, he did start one game in each playoff series with Boston, winning one. 

In 2014, Peavy had a dismal start to the year with the Red Sox, going 1-9 with a 4.72 ERA in 20 starts before being shipped to the Giants. The change of scenery was beneficial to both Peavy and San Francisco as he went 6-4 with a 2.17 ERA in 12 starts. While his postseason stats were once again not pretty with a 1-2 record and 6.19 ERA, they were good enough to help the Giants secure another championship.