Some comments I have...
Massu vs Gaudio - Nicolas can be a great player when he plays up to his potential. As that happens rarely, he can never get as far as he could. He already had three great matches in a row, so maybe he will turn off this time. Gaudio, otoh, is having an incredible year on clay courts, so I guess he gets the edge if the match goes to a third. I´d pick Gaudio in three sets.
Costa vs Corretja - damn, I want to watch this!!! Well, its a classic on clay. Its supposed to be a great match. I will pick Albert to win because he is a monster in this Kitzbuhel tournament. He won like 2 or 3 times already, reached plenty of semis and is on a better year.
Zabaleta vs Pavel - In theory, Mariano is a better player on clay. I say in theory because Andrei is a master of beating faves. I wont pick anyone, dont wanna burn my tongue.
Chela vs Ferrero - Well, Juan Carlos would be the obvious pick. He achieved a degree of maturation in his game that Chela didnt yet. BUT Juanqui´s year is not at all good. That will even things a lot. If Chela can manage to keep on focused and play what he knows, Ferrero´s slump can pay a big role. But I got this feeling that this wont happen. Ferrero in straight sets.
Gaudio in 2 sets.
Corretja in 3 sets (this is more wishful thinking than prediction).
Pavel in 2 sets (he's doing really well lately).
Ferrero in 3 sets. Is it true they've never played each other before?