On paper, it's really hard to see upsets in the Federer, Nadal and Djokovic matches. Unless Anderson plays out of his mind, you'd think Federer will be able to neutralise him and start moving him around more than he's comfortable with. Delpo having no rest day probably means that, likewise, unless he comes out and blows Nadal off the court in 3, then he's likely to suffer. Though, Rafa is now my tip to win the whole thing, so I would say that. I just can't see Nishikori hurting Djokovic on grass over 5 sets. The Isner v Raonic match might be the most competitive, albeit probably not amazing to watch.
Having said all of that all of the faves will probably lose in straight sets and immediately retire from all tennis in shame.