Nelson (shoulder) threw a bullpen session Saturday, Adam McCalvy of MLB.com reports.
Prior to Saturday, Nelson had managed to play catch off a mound, but he hadn't advanced to pitching. Although a return this year seems unlikely, it's good to see that he's continuing to make progress. If Nelson doesn't return from the disabled list before the season ends, expect him to throw in the instructional league or Arizona Fall League during the offseason to ensure he's ready for the 2019 campaign.