The Giants claimed Whitcomb off waivers from the Astros on Thursday and optioned him to Triple-A Sacramento, Alex Pavlovic of NBC Sports Bay Area reports.
Whitcomb will reclaim a roster spot after being booted off the Astros' 40-man roster Monday, though he will remain in the minors for the time being. Trevor McDonald (elbow) was transferred to the 60-day injured list in a corresponding move.