A follow-up MRI exam on Monday revealed that Bumgarner's sprained left shoulder will not require surgery, but the Giants are bracing to be without their left-handed ace for two months.
Giants general manager Bobby Evans said before Tuesday's game against the Dodgers there is no definitive timetable for Bumgarner's return even after the MRI was read. A more detailed schedule for treatment and Bumgarner's eventual return is likely to become clearer in May.
The former World Series MVP sustained bruised ribs and a sprained AC joint in his pitching shoulder in a dirt bike accident during last Thursday's off day in Colorado. He will wear a sling on his pitching arm for at least another week.
"Our focus is getting him healthy," Evans said.
Bumgarner never previously was on the disabled list during his eight-plus major league seasons.
He said Monday 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. "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."
Bumgarner, 27, is 0-3 with a 3.00 ERA this season.