This is the first time since Wimbledon 2007 that Murray has missed a Grand Slam event. It was expected, but it is for the best as it was clear based on his previous clay performances that he really did not have a great shot at the RG title. As for Del Potro, a decision will be reached tonight or tomorrow morning as to whether he will play.
If JMDP does NOT play, then the top seedings for RG will go something like this:
1. Djokovic, Novak
2. Federer, Roger
3. Nadal, Rafael
4. Ferrer, David
5. Berdych, Tomas
6. Tsonga, Jo-Wilfried
7. Gasquet, Richard
8. Tipsarevic, Janko
BTW - I think actually Wawrinka has confirmed that he's not playing RG either