I wonder why Ivanisevic did much better indoors than Roddick when they are superficially similar players (yes actually rather different other than the booming serve but how exactly does this work out?)
@metsman could you help us with this as well?
Goran is overall a fast courter through and through, Roddick isn't quite (not that he's a slow courter, I'll explain in more detail).
Goran had better feel and thus was better suited to the slick indoor game where rallies are extremely fast (but there are still quite a few rallies!) Roddick is actually not a guy who loves very fast rallies. He likes grass because serves are harder to return on grass than indoors and grass has very few rallies. Indoors is probably the truest overall test of fast court prowess, just a serve alone won't be enough to bring success like it could to an point on grass, you need a complete fast court game. Goran was a natural fast courter through and through despite his weaknesses. Roddick's identity really wasn't as a fast courter, yes he had a great serve and forehand (at least at some points) but his style of play was built for outdoor courts all the way where the elements slow down the speed of the game. Look how much Roddick liked Miami for instance, as a junior Roddick was very much a grinder with a big serve. He could pop the FH, but also loved a gritty behind the baseline physical game. This is why I think it's laughable when people say Roddick would be tougher than Federer on true fast courts, yeah the serve would be a handful but in every other part of the game Federer is a significantly more natural fast court player. He loves low bounces, playing fast and has some of the best reflexes ever. Even today he looks like a totally different player when he goes to Basel. Roddick likes a serve dominated game, yes, but if he has to rally he'd much rather rally on even a slower outdoor HC than a slick and fast indoor court.
Let's not forget that Roddick played with fairly extreme grips and wasn't comfortable with the transition game, these are not the hallmarks of a great indoor or low bounce player. Yes it worked on grass because his serve was so effective on grass and grass sees fewer extended rallies(and modern grass probably bounces higher than slick indoor courts anyways). I also think rallies on grass are slower than rallies indoors because the bounce is (was) so uncertain on grass that things have to be more measured if you are playing from the baseline. Indoors forces more rallies and due to the sure bounce you can just swing away and thus you need to be very comfortable with very fast extended rallies and a low bounce, Roddick wasn't.
However, there's also a factor of Roddick almost always being worn down by indoors season. The 03-04 TMCs weren't even indoors but he had disappointing losses in both. Goran made very sure to peak for Wimby and indoors (although he wasn't at all bad on clay, USO was where Goran was really tragic but he's just not mentally cut out for the environment, stark contrast to Roddick obviously). Roddick actually usually did better in the early season indoor events (San Jose and Memphis, heck even won in Lyon on carpet).