The Diamondbacks placed Nelson on the 15-day injured list Saturday with right shoulder inflammation, Jesse Friedman of GoPHNX.com reports.
Nelson surrendered five earned runs over just 4.2 innings during his most recent outing Sunday, and his shoulder troubles may help explain his poor performance. The Diamondbacks are hopeful he'll be able to return to the rotation after a minimum-length stay on the injured list, though he won't be eligible for activation until the final series of the regular season. Until Nelson is back in the fold, Arizona will likely move Jordan Montgomery from the bullpen back into the rotation.