Nelson (elbow) threw 25 pitches in the bullpen Friday, Alex Weiner of Arizona Sports reports.
Nelson began his bullpen progression Friday. If the right-hander comes out of Friday's session without issue, he'll throw another one Tuesday. The Diamondbacks are leaning toward bringing Nelson back as a reliever, which will require a shorter ramp-up, as injured starters Corbin Burnes (elbow) and Zac Gallen (elbow) are ahead of him.