What is the reasoning behine the moves here?

Hi all,

In this game Kotov - Matanovic:

Black elects to move ...b6

Why would he not  ...Bxa4?

To me it looks like it's hanging. How would this move weaken the black position?

Thanks.

I'll give you a hint.  After Bxa4, it is a relatively simple tactic you are looking for.  If you get stuck, list out the things that the bishop was doing before it moved.  

Slowdancewitihme is likely correct about the motive for b6, but bxa4 flat out fails.

I'm thinking:

... Bxa4

Nxe5   fxe5 (to avoid Qg7#)

Qxe5+ and the rook is lost.

Close enough. I'll give you that one.

1. ... Bxa4

2. Nxe6 fxe6

3. Qxe6+ Qf7 (the only way to save the Rook)

4. Qg4+ picking off the a4-Bishop.

Got it. Thanks very much - the book didn't explain that.

This is an interesting alternative when I used the Houdini engine to look at it:

1. ... Bxa4

2. Nxe6 Qe5

3. Qxe5 Rxe5

4. Nd4