The left-hander threw a 30-pitch session on Sunday -- his second bullpen in three days -- and is slated to throw live batting practice to his teammates during a four-game road series against the Colorado Rockies that begins on Thursday.
Ironically, it was during a trip to Colorado in April when Bumgarner was injured. The Giants had an off-day in Denver on April 20 when Bumgarner injured the shoulder as well as some ribs in a dirt bike accident.
Four days later, Bumgarner said he regretted the decision to ride trail bikes in the mountains outside of Denver with two family members.
"Obviously, it was not my intentions when we set out to enjoy the off-day," Bumgarner said at the time. "I realize that's definitely not the most responsible decision I've made. It sucks not being able to be out here with my guys."
The original timetable was for Bumgarner to miss six-to-eight weeks but he won't be returning to the majors in June. The Giants plan to have him make five minor-league rehab starts and don't expect him back with the big-league club until after the All-Star break.
The 2014 World Series hero had never previously been on the disabled list during his eight-plus major league seasons.
Bumgarner, 27, is 0-3 with a 3.00 ERA this season.