The scrum half situation just seems really fluid. Obviously Robbo is #1, but behind him I have no idea whatsoever what the order is and I'm not sure Blackers does either. That's not a criticism by way, there is nothing particularly good about pre-conceived pecking orders, and we've seen other positions - for example hooker and loosehead - perhaps benefit from fluidity and competition.
What I don't buy is the idea that Vellacott is still a nailed on #2 but has been rested. If you have a nailed on #2 you don't rest him when your #1 is away, you play him because he isn't going to forgive you if you don't. So, he's either been carrying a niggling injury that has not been mentioned, or Blackers has genuinely opened up the position to competition from the 2 youngsters. Personally I hope it's the later, not because I don't like or rate Vellacott but just because I don't see him ever becoming another Robson - a genuine game-changing point of difference. It's too early to tell whether Wolly or Porter can be that either, but with Porter in particular I like the signs and I'd love to see a bit more of what he can do.