Walker (foot) was placed on the 15-day disabled list Wednesday, Ryan Divish of the Seattle Times reports.
The young right-hander aggravated his pre-existing foot issue during Tuesday's start, leading to him scheduling a meeting with a foot specialist for later in the week. He's officially landing on the disabled list due to right foot tendinitis, which leaves a spot open in the rotation for this weekend. The hope is that the upcoming All-Star break and additional rest time thereafter will be enough for Walker to get back on the hill before too long, but a more concrete timetable for his return figures to be released in the coming days.