This should have been match of the tournament from R4 definitely, but right now it didn´t look so great, Berdych today had some leg problems, and Delpo seems to be not 100% fit since Rome.. so the fitter one will win, i am really angry, because Fed is loosing here sets with nobodies, so healthy Tomas or healthy Delpo can take him down, but neither of them is probably 100% healthy.
Tomas is healthy, just very tired, has played non-stop for many weeks in a row.
Don't think the winner of the match will beat Federer in the following round. Del Potro would stand a better chance, but he'd obviously need to be completely fit and get over the mental block he has developed against Federer since his comeback, both unlikely.
Tomas can hit through Federer in normal conditions, but he seems so tired, his scheduling wasn't good at all. But I guess he might have some energy reserves, you never know. But I don't think either of these guys is stopping Federer, wouldn't put my money on it for sure.