Andrew Miller’s tenure in Boston got off to a rocky start. The Sox actually non-tendered him less than a month after acquiring him, but then re-signed him days later.
His struggles in the starting rotation and injury in 2012 prompted the Sox to move him to the bullpen, a role in which he thrived. However, injuries continued to limit him, and the Sox traded him to the Orioles at the 2014 deadline for Eduardo Rodriguez. After pitching excellently in Baltimore, the Yankees swooped in and gave him a four-year contract ahead of the 2015 season.
Adam Ottavino mostly makes this list because he famously bragged that he could strike out Babe Ruth.
Ottavino is also rare trade between the Sox and Yanks, only the second deal since 1987.
After playing on several Red Sox postseason teams, including their 2018 championship squad, Andrew Benintendi is now a Yankee.