Indeed Seattle shortstop J.P. Crawford, who posted 4.9 fWAR this year in his age 28 season, remains under contract through the 2026 season.
And four of Seattle’s top seven prospects are shortstops, including 18-year-old Felnin Celeste’s, the overall No. 2 prospect in a recent international class.
The Mariners would be unlikely to trade their top prospect, 20-year-old shortstop Cole Young, straight up for Marcelo Mayer (and the Red Sox likewise would be unlikely to do that deal).