Walker left Tuesday's game in the fourth inning with an aggravated right Achilles' tendon, Shannon Drayer of 710 ESPN Seattle reports.
The right-hander's velocity dipped into the low-90s in the fourth inning and he was lifted after his 65th pitch of the night. There is no arm or shoulder injury to report, but Walker's status for his next start and the next several turns probably won't be known until he undergoes further testing. Edwin Diaz replaced Walker with one out in the fourth.