Nelson (back) was reinstated from the 15-day injured list Thursday.
Nelson has been out for the past month due to back spasms, but he'll rejoin the Diamondbacks on Thursday after making one rehab appearance with Triple-A Reno. The 26-year-old has eight holds with a 1.57 ERA, 0.90 WHIP and 27:8 K:BB across 34.1 innings this year and should re-enter the high-leverage mix now that he's healthy.