Justin Turner
This is a tough one because Justin Turner played well for the Red Sox this season. In 558 plate appearances for Boston in 2023, he put up 2.1 rWAR and a .276/.345/.455 slash line with 23 homers. He is not the same player he was during his prime with the Dodgers, but the guy can still flat out hit and seems to have been a positive influence on the Boston clubhouse this season.
The problem is that Turner has a player option worth $13.4 million for 2024 that also has a buyout worth $6.7 million. While Justin did seem to enjoy playing in Boston and the Red Sox would likely prefer for him to stick around, he also could probably make more by not exercising his option, taking that buyout, and then signing with a different team this offseason. Boston may not mind too much if that happens as that could make some roster/DH considerations regarding Yoshida, Casas, and others easier to manage, but it would be sad to see him go nonetheless.