Walker was placed on the 10-day injured list Wednesday with right oblique soreness.
The first baseman just returned from the IL on May 3 after a strained right oblique sidelined him for nearly a month, so this latest development could mean an aggravation of that injury. Walker, hitting .203 on the season, recorded a hit in six of his seven games after returning from the first IL stint. Infielder Andrew Young was recalled to replace Walker on the active roster.