I rate them all quite highly, but lets be honest, they're injuries are becoming a pain in the arse. Even under SAF it was a problem, but he had Rio and Vidic still performing well. This season, the Rio/Vidic partnership has been completely broken and it's sad to see. Again though, you can't blame Moyes for key players declining.
We aren't witnessing the end of an era solely because they've hugely declined this season, but it's safe to assume that it's a big part of the problem. Those three players are a huge part of what we were all about, they were part of a very strong core. I actually think that some people are daftly underestimating the importance of them.
There is a difference between players ageing, and players declining.
When more than half of the team is declining (old and young) the finger will have to point at the manager rather than the players.
Especially in defence, it's all about the system, and organization. There were always players who were under-performing under Fergie, but then he'd find an alternative way or cover, or managed to pull them out of their slump..
Did we forget Ferdinand's awful display against City in our 4-3 win? That was in 2009! Rio and Vidic has never been the rocks they were for us in 2007/2008. But we knew how to use them, rotate them, and replace them when needed.
And like I said, we had even bigger injury problems when SAF was in charge. We even had to play Carrick at CB at times. But in all those times SAF still manage to control the situation, and find the appropriate solution, and what made that possible for him is because we had a very good and big squad.
Don't see how everything would have suddenly changed 4 months later.