It is easy to forget how well Rodriguez did in Amstel last year. No one could follow his attack on Cauberg except Gilbert, and he was well ahead of Gerrans at the finish line. And we all know that he is in excellent form after two stage wins in Vuelta Pais Vasco.
So, who can really threaten J-Rod if it comes down to a showdown on Cauberg? I see four possible challengers, two of them more so than the others.
Gerrans - Great form this year, 3rd last year. He won't be able to follow an attack from J-Rod, but could catch him when in flattens out in the end. Tactical rider.
Gilbert - Winner last two years after total domination in the final both years. Not very good form this year, but it might be improving. If he even gets near last years form he will challenge Purito. Cauberg is a perfect final for Gilbert and last two years should give him great confidence. Still, Gilberts form is uncertain, and he might not even be there in the end.
Valverde - Great season so far. He missed Vuelta Pais Vasco as a good build up, but came 2nd in Klasika Primavera de Amorebieta last sunday. Has the punch and speed to maybe match an attack from Purito.
Sagan - Super season so far, has taken the next step and really shown that he is already a great classics rider and a future winner. In a race under 200k Sagan would probably destroy J-Rod on a final like Cauberg, but in a race with 32 climbs and over 250k, it might be more doubtful.
Given form and sprint capacity on a final like Cauberg, I believe that Valverde and Sagan are the greatest threats to Rodriguez, with Gilbert and Gerrans just behind.
This doesn't mean that I think top 5 will consist of Purito and the four challangers, just that these four are the riders with the capacity to actually beat J-Rod on Cauberg. Other riders wanting to win should try to go solo or drop J-Rod before Cauberg.