I can't believe it's a mountain stage! Yes, I just wrote a long post about how boring the Vuelta is, and I suspect today will provide more supporting evidence. But it's not out of the question that sparks will fly.
The temptation to expect GC racing on the road to Ávila is due to the presence of the Puerto de Mijares, a 20km cat-1 hump averaging 5%, and the Puerto de Navalmoral, another 20km or so of intermittent ascension. But the finish is another 35km from the latter summit, mostly on flat roads. And tomorrow is something of a climb-fest. So if you're Carlos Sastre and you're feeling frisky, is today really the day to try something? Finishing off those last 35km in a small escape would be highly costly, and not nearly as likely to produce as an escape over Friday's many hills.
Another possibility is a large field that conveniently splits in between Sastre or Efimkin and Menchov/Evans/Sanchez. Such splits are harder to close when the front group is large and motivated. But Menchov would have to either be asleep at the switch, or running on empty, and if it's the latter it still makes much more sense to try pinning back a bigger chunk of time Friday instead.
About the only potential intrigue that I actually expect comes from the points race. The Mijares won't threaten any of the protected riders or their helpers, but it will likely cause the development of an autobus at the back. Will Petacchi shelter there? Does his answer change if Bennati tries to stay with a forward group? Who knows. But I predict some of the fastmen will be straggling in pretty late, while a large group including all the GC favorites comes in together.