Its not the conditioning thats the problem.
If she plays doubles, she will have no time to prepare (practice the areas which need fine tuning, practice according to her opponent's strength and weaknesses, make sasha play like Azarenka etc.) for her SF match. Preparing for the match doesnt mean just resting and going out on court and hitting a few balls.
I hope Serena withdraws.
My interpretation of the post I was responding to was that the poster felt it would be too much of a physical/mental strain on Serena to play 1 and a half matches before her semifinal, so that's what my answer was about. :shrug: It's not even a guarantee that she will play 1 and a half matches today anyway.

I think she will be fine against Vika, I mean Sascha can scream and wear Capri pants under a dress

if he wants to (sorry I just had to get that joke in

) to help Serena, but I think she's more than ready to face her with or without that. Serena has only pulled out of Doubles when injured in recent years. I don't think Venus would be terribly upset if she did pulled out of doubles to preserve her chances in singles, but Serena just won't do that. It's just not her mentality. :shrug: