Harrison is slated to start Friday's game against the Marlins in Miami.
After getting called up from Triple-A Sacramento on May 4, Harrison initially worked out of the bullpen, but he moved into the rotation last week following Justin Verlander's (pectoral) placement on the injured list. Harrison took a loss to the Nationals in his first start with the Giants last Saturday, giving up two runs in four innings while striking out four batters. The lefty should have a longer leash in his second start after tossing just 57 pitches against Washington, but he may not be guaranteed any turns through the rotation beyond Friday. Verlander threw a 40-pitch bullpen session Tuesday and could be ready to return from the IL as soon as next week.