Have to imagine that's pretty big news with Purke going and not Rendon. If they aren't taking any chances with a position player like Rendon, then they certainly wouldn't gamble with Purke if he was not 100%. Not only 100% healthy, but 100% he's good with his mechanics as well. Since they want to improve Rendon's mechanics before game experience, they definitely wouldn't throw Purke out there if he wasn't consistent with his mechanics so far.
While it's a bit disappointing for Rendon, it's not a big deal. But I think it's really positive news for Purke.