What trade market lurks for 49ers’ backup quarterback Mac Jones?

Mac Jones could be the 49ers’ best trade asset in years, should they choose to part with Brock Purdy’s backup whose efficient play and uplifting spirit bailed them out early last season.

Six years ago, the 49ers went to the scouting combine and shopped All-Pro defensive tackle DeForest Buckner, who would fetch a first-round pick from the Indianapolis Colts.

Jones likely won’t command a first-round pick, or perhaps even a second-rounder. Supply and demand will dictate his value on the quarterback market...