I've been thinking a bit more about this and the idea that the sequence 14.Nb5 b6 15.b4 a6 16.Nc3 Rf7 is somehow best play for White is totally ridiculous (and I'm not exaggerating)
let's compare the position after 13...Ng6 and the one after 16...Rf7:
- White has made one move (b4), while Black has made three (Rf7, b6, a6)
- b4 is only useful in preparing c5, without that it is generally a harmful/weakening move because it blocks the white queen after Qb3, and a queenside pawnstorm is about the most useless thing White can do (because as you know, Black is attacking some vitally important piece)
- but c5 didn't need to be prepared anyway, 14.c5 is a good move and White manages to draw here (

) because 14...Nxc5 15.b4 Na6 is more or less forced and the knight is too far away from where it wants to be (f6) and g4 is difficult to prepare
- let's suppose Black plays b6 after this and now it can be argued that Black's b6 is actually more useful than White's b4 because after 14.b4 b6 15.c5 (what else?) Black can play 15...Nf6 because after 16.cxd6 cxd6 17.Nb5 there is no pawn hanging on a7 (not because this pawn is so important but a knight on a7 attacks the light-squared bishop, which is essential to push the g-pawn)
- but it gets even worse: White has simply passed two moves, maybe he was looking at the computer evaluation and out of generosity wanted to give Black some chances to survive
- Black on the other hand played a6, a moderately useful move because it stops Nb5; one might argue that b6 is weakened now but there's still a pawn on c7 (without that, Na4 can be irritating) and the only way to do something about that involves playing c5, after which the b6-pawn can be exchanged anyway
- moreover Black played Rf7, which is 100% useful: it covers c7, it prepares a future Rg7 or Rh7, and it makes room for Bf8 (but sometimes this isn't necessary and Bh6 can be played)
so it wouldn't surprise me at all if Black is objectively winning after this
TonyRo wrote on 07/29/14 at 17:20:08:
If you're active in CC, you may have two approaches: that an easy draw with Black is exactly what you want, and that pressing your luck against a competent White player is risky, or that you'd rather just complicate the game as much as possible and go for the win.
a competent White doesn't play this line
and it would be a complete shame not to try to win when your opponent plays the Mar del Plata, simply analysing these lines can be very fun, I still remember stuff like Houdini going from +2 to -9 in mere seconds