Walker was diagnosed with tendinitis in his right foot, Ryan Divish of the Seattle Times reports.
Walker underwent an MRI on Tuesday, and though there was no structural damage revealed, it sounds as though his status for his scheduled start Friday is in some jeopardy. After experiencing discomfort his last time out Sunday, the 23-year-old remains without a precise timetable, but a DL stint remains a possibility if he is forced to miss his next start.