Walker told reporters that he felt discomfort in his foot from his first pitch on Sunday against the Red Sox, the Seattle Times reports. He was removed as a result of the ailment after 88 pitches despite throwing five scoreless innings.
It's unclear if Walker will need prolonged rest before his next start, and a stint on the disabled list may be on the horizon. Walker was sore in between starts after leaving his previous outing due to the injury, but the Mariners' rotation depth has been thinned out recently with Wade Miley joining Felix Hernandez on the DL. The team's plans for Walker should become clearer later in the week, but Donn Roach and recently acquired right-hander Zach Lee are among the candidates in the mix for a promotion if Walker misses time.