Nelson is likely to pitch Saturday in San Diego, either as a traditional starting pitcher or bulk reliever, Nick Piecoro of The Arizona Republic reports.
He'll be filling in for the injured Corbin Burnes (shoulder). Nelson is not stretched out to handle a normal starter's workload, as he just returned in a relief role last week after missing more than three months with a right elbow strain. Because of that, it will essentially be a bullpen game for the Diamondbacks.