Diamondbacks manager Torey Lovullo said Wednesday that Nelson (elbow) will begin a rehab assignment with Single-A Visalia on Saturday, Alex D'Agostino of SI.com reports.
Lovullo also noted that Nelson -- who has been sidelined since late June with a right elbow strain -- is likely to be used out of the bullpen when he returns. Coming back as a reliever should shorten Nelson's rehab assignment, though he figures to require additional rehab outings after Saturday.