Carlsen-Ivanchuk sicilian question

Another of my "how come?" type questions..

GM Christian Bauer says f3 is "forced" here but I can see a couple ways to defend e4 (assuming I'm right that Bxc3, Nxe4 is the threat): Bd3 is most obvious and I even found a game with it: http://www.chessgames.com/perl/chessgame?gid=1521970

Guessing again, might be something more concrete but maybe Ng4 would be annoying? White doesn't want to give up the dark squared bishop.

Put some more thought into it and I guess Wht must also protect against Ng4?

Guessing Bd3 blocks the d file, and black's dream break is d5 in these structures.  Bd3 cuts off two pieces worth of influence and is a passive diagonal to boot.

Just my interpretation.

you spoke just about 15 minutes too soon ;)

9...Ne7 was the interesting choice later. Judit Polgar played this in one of the previous candidate tournaments and lost both of the games. 9...Ne5, or 9.0.0 have been more popular.