The Giants optioned Warren to Triple-A Sacramento on Saturday, Alex Pavlovic of NBC Sports Bay Area reports.
Warren made three appearances with the Giants after being recalled from Triple-A on Sept. 6. Over that span, he allowed two runs on four hits and two walks while striking out two across 4.2 innings. The move makes room on San Francisco's 28-man roster for the reinstatement of Jordan Hicks (shoulder) from the 15-day injured list.