Nelson was placed on the 15-day injured list Wednesday with right scapula inflammation.
Nelson had X-rays come back negative after he was struck by a comebacker in the right forearm during Sunday's start against the Padres, but he's now headed to the IL with a inflammation around his shoulder. The 24-year-old will be eligible to return for the last couple days of the regular season, though it's unclear if he's expected to be ready to pitch by that point.