I don't think Tsonga should be suffering from any lack of freshness. If he is, he's poorly conditioned. He's dropped 3 sets in five matches. I don't think the fact that a player plays a five set match two days ago means he should be tired today. He's an athlete, and a physically strong bloke. If he's tired after the Nishi match, then he hasn't been training properly for grand slam tennis.
But how he handles himself will be interesting. I remember the Ferrer match very well, and the only way I could describe his display was that it was cowardly. I know, that's harsh, but he's not an inexperienced kid, and he totally ran away from his responsibilities to himself in that match. I believe he did the same thing at the Davis Cup, more or less sacrificing the hapless Gasquet to play Federer, instead of getting out there himself.
These things are not good portents for today. I expect Stan to enjoy this one a lot...