The field was deeper when Fed started to rise and before this risen than it is now.
Djoko emerge = Safin + Hewitt + Roddick emerge at 2000 - 2002. The difference is that the field was deeper and there were still surface specialists since the courts were really diferent at that time. Safin and Hewitt were good enough of hard courts but at grass and clay there were specialist who despite being old or injured could play well there.
Djoko has no real opossition now that Fed is Old and Nadal is injured and the surfaces are just the same all over the year.