While a deal doesn't appear imminent, discussions have advanced to the point that Milwaukee is talking internally about what it's willing to give up, Morosi reported.
In initial trade talks with the Brewers, the Giants indicated a young starting pitcher such as Corbin Burnes, Brandon Woodruff, or Freddy Peralta would need to be part of a deal for Bumgarner, Morosi added.
Although his name has been circulating in rumors throughout the winter, it was reported in December that the Giants are less likely to deal Bumgarner - who will become a free agent next offseason - than they were shortly after the 2018 season ended.
If Farhan Zaidi, the Giants' new president of baseball operations, chooses to part with the left-hander now, Milwaukee is emerging as his most likely destination, according to Morosi.
The Brewers reached the NLCS in 2018 despite fielding a patchwork starting rotation and liberally using the en vogue "opener" strategy throughout the postseason. The return of Jimmy Nelson from shoulder surgery should bolster their staff in 2019 and make it more stable, but the rotation as a whole remains the NL Central champions' weak spot.
Bumgarner, a World Series MVP in 2014 and three-time champion in San Francisco, is the ace that was missing from the Brewers' staff last year. Adding a healthy Bumgarner could make Milwaukee the favorites to win the franchise's first pennant in 37 years.
The 29-year-old has started just 38 games over the last two seasons because of injuries, and he was limited to 21 outings last year. When healthy, Bumgarner remained his steady self in 2018, posting a 3.26 ERA, 3.99 FIP, 1.24 WHIP, and 109 strikeouts over 129 2/3 innings.
Bumgarner will draw a $12-million salary next season after the Giants picked up his club option earlier this winter.