Alvarez (shoulder) is expected to begin a rehab stint with High-A Stockton on Wednesday, Susan Slusser of the San Francisco Chronicle reports.
This marks a big step toward returning to the big leagues after Alvarez suffered a partial UCL tear last May, but the A's are expected to take it slowly with the 26-year-old. They're currently targeting a late-May or early-June return, but the timetable could change depending on how Alvarez feels following his first game action.