Per The Athletic's Andrew Baggarly, team president Farhan Zaidi is indicating to interested clubs that the Giants "will get the value they are seeking or they won't move [Bumgarner]."
For a Giants team that enters Tuesday last in the National League West with a 26-38 record, Bumgarner is presumably their best trade asset leading up the July 31 deadline.
The four-time All-Star is only making $12 million in 2019, the final season of his contract before becoming a free agent. He's rounding into form after a slow start with a 3.47 ERA and 49 strikeouts in 49.1 innings over eight starts since May 1.
Given the state of the Giants right now, as well as their future financial commitments, it would be in their best interest to try collecting at least one top-tier prospect in exchange for Bumgarner. They are currently set to pay 16 players $136.9 million in 2020, per Spotrac.
The danger for the Giants is any team interested in Bumgarner will only be trading for, at most, three months of control. Recent history has shown teams aren't going to give up significant packages for players who are on the verge of hitting free agency.
Last year, for instance, the Baltimore Orioles received five players from the Los Angeles Dodgers for Manny Machado. Not one prospect who went back to the Orioles ranked among the top 100 in Major League Baseball entering 2018, per ESPN.com's Keith Law.
San Francisco is on pace for its third straight losing season, despite having a top-five payroll every year since 2017.
Since it's unclear what the Giants want in return for Bumgarner, it's impossible to say they may have to settle for a deal just to accrue future assets. But the odds of them receiving at least one elite prospect in return would seem to be slim at this point.