Alvarez (shoulder) will throw a full bullpen session on Tuesday, Susan Slusser of the San Francisco Chronicle reports.
Alvarez threw off a mound a week ago for the first time since July and has continued progressing to a return. If all goes well during the bullpen session, the next steps to watch for will be when he sees live hitters, then game action. The initial timetable for the 25-year-old was said to be June, but it's looking more and more possible he could make his return to the rotation sometime in the early months of the season.