Nelson (shoulder) was cleared to begin throwing breaking balls and had a mound session prior to Tuesday's game against the Dodgers, Adam McCalvy of MLB.com reports.
Nelson is currently working his way through the throwing program but isn't expected to return prior to September. Progress has been slow for the 29-year-old, and he will need significant mound work in order to build up his stamina enough to be a viable option for the Brewers this season.