I can't imagine Agassi playing two crap matches in a row. I definitely think he's the favorite against Ancic. From what I saw on Friday, Ljubicic is a far better player than Ancic, who for some reason wouldn't come to the net even though Roddick was destroying him in baseline rallies. Ancic will have to play the best all court tennis he possibly can in order to beat Agassi, and I see no reason to believe that's going to happen. Likewise, if Agassi isn't motivated to come to this match fired up, then he's probably lost fire for the game period.
The toss up is the Roddick/Ljubicic match. IMO that's the key match. This will be a good test for Ivan, who I think can be top 5 by the end of the year. If he beats Roddick it'll prove he can be top 5 because despite Roddick's limitations, he's undeniably a legitimate top 3 player.
The person who serves better will win. From what I remember, Roddick didn't serve particularly good against Ancic. He won that match because Ancic didn't have a game plan, seemed intimidated by the crowd, Roddick's cockiness, and by representing his country. I don't think Ivan's going to be intimidated. He just won two matches and he's got to be as confident as he's ever been. If he can play Federer tight, he's gotta believe he can beat Roddick.
The Bryan bros' loss is not that big a surprise. It's not like they lost to two baseliners. Ancic probably has better volleys than both of them, and Ivan is very comfortable at net as well. Throw in the fact that the Croatians both have bigger serves and it's not that surprising.
I predicted an upset and although I'd love to be proven wrong, it's not looking good for the USA. Roddick is going to have to play his very best to beat Ivan.