The Nationals placed Gallo on the 10-day injured list Wednesday with a left hamstring strain.
Gallo exited Tuesday's 5-4 win over the Tigers due to the injury. The Nationals haven't revealed the grade of Gallo's hamstring strain, but the injury is clearly significant enough that he won't be available for at least the next 10 days. Trey Lipscomb was called up from Triple-A Rochester to replace Gallo on the 26-man active roster and will be an option at first base along with Joey Meneses.