Per USA Today's Bob Nightengale, the Giants haven't ruled out extending Bumgarner, but they also "recognize it may be a long shot" and no talks have been had between the two sides.
It's looking more likely that the Giants won't deal Bumgarner prior to the July 31 trade deadline.
Per MLB.com's Mark Feinsand, the Giants are "all but certain" to retain the four-time All-Star for the rest of the season and could become buyers if their weekend series against the San Diego Padres is successful.
San Francisco has had a dramatic turnaround after looking like an afterthought in the National League. The team was 12 games under .500 as recently as June 29 but has since won 17 of the past 21 games.
Bumgarner has lowered his ERA from 4.20 to 3.66 in 12 starts since May 23. He has 70 strikeouts and 66 hits allowed in 70.2 innings during that span. The 29-year-old is in the final season of his current contract and can become a free agent this winter.
The Giants enter Friday with a 52-51 record, tied with the Arizona Diamondbacks for second in the NL West and 3.5 games behind for the No. 2 wild-card spot.