They will have no issue getting Sproat on, if necessary, since he would be an “injury replacement” for any number of players who would otherwise be eligible if not for injury — Minter, Canning, Kranick, et al. You may recall that Max Kranick himself was on the wild card round roster last year despite having never yet appeared for the Mets in the majors. The August 31 deadline is to have the player in your organization for eligibility. Which is why the Phillies had to get Buehler by then, the Cubs with Santana, etc.