Garver was scratched from the Mariners' lineup before Friday's game against Boston due to back spasms, Gabrielle Starr of the Boston Herald reports.
Garver is officially listed as day-to-day, so his back shouldn't keep him out for very long. The 33-year-old veteran went 1-for-4 with a double in his Mariners debut Thursday and will operate as Seattle's primary DH this season.