Alvarez (shoulder) is expected to throw 60 pitches or four innings in a rehab start for High-A Stockton on Saturday, John Hickey of the Bay Area News Group reports.
Alvarez is set for a big step forward after throwing just 40 pitches in Monday's rehab outing for Triple-A Nashville. He's still at least a couple weeks away from joining the big club, but it does appear Alvarez is on track for a debut by the end of May. Previous reports suggested that he's expected to be ready in late May or early June.