Walker will be sent to see a foot specialist after he left Tuesday's game with discomfort in his right foot, MLB.com's Greg Johns reports.
It sounds unlikely that Walker will make his next start this weekend, as both the team and the player seem intent on getting to the bottom of his foot issue. He threw just 67 pitches before leaving Tuesday, and admitted that he felt discomfort when he was warming up in the bullpen, but attempted to pitch through the pain. Assuming Walker is unable to start Sunday, the Mariners could opt to go with a bullpen game in advance of the All-Star break or they could dig into the Triple-A rotation, although there are not any notably intriguing arms at that level.