Belt (side) is not in the lineup Wednesday at Arizona, Maria I. Guardado of MLB.com reports.
The Giants were considering sending the 33-year-old for an MRI after left side discomfort resurfaced during Tuesday's contest, so it's hardly a surprise he's out of Wednesday's lineup. Belt should be considered day-to-day for now, but he could be forced to miss some time after missing six consecutive games due to the injury last week.