Turning to veterans, who has more value: Boston's J.D. Martinez or Seattle's Kyle Seager?
According to Baseball Trade Values, Martinez has a median trade value of a negative $8.6 million and Seager a median trade value of a negative $13.5 million:
https://www.baseballtradevalues.com/
Martinez, who is two-and-a-half months older than Seager, is owed $19.375 million each in 2021 and 2022. He may opt out after this season.
Seager is owed $18 million in 2021 with a buyout of up to $3 million of a 2022 option of $15 million to $20 million (depending on incentives).
In 185 games* since the start of the 2019 season, Martinez has posted 2.7 fWAR, valued at $21.6 million. In 149 games since the start of the 2019 season, Seager has posted 4.2 fWAR, valued at $33.4 million.
Martinez posted a higher fWAR in 2019 with 3.2, valued at $25.7 million, in 146 games while Seager posted 2.9 fWAR, valued at $23.5 million, in only 106 games.
In 1,107 career games*, Martinez has posted 23.6 fWAR, valued at $187.8 million. In 1,304 career games, Seager has posted 32.0 fWAR, valued at $245.2 million.
https://www.fangraphs.com/players/jd-martinez/6184/stats?position=OF
https://www.fangraphs.com/players/kyle-seager/9785/stats?position=3B
* not counting Thursday's 0-for-4, three-strikeout performance