Stigma wrote on 04/15/10 at 20:20:02:
6...Bd7 isn't really necessary, White is often happy to drop the queen back to c2 anyway. There is a tempo fight going on in these positiions: Black wants to play ...dxc4 followed by ...e5, but only after White spends a tempo with his light-squared bishop. In the meantime, 0-0, a6 and Re8 are all more useful moves than Bd7.
Right, hence why 6...0-0 is supposed to be the main move.
It's not even clear how 6...Bd7 is useful, since 6...0-0 develops and serves the same purpose of breaking the pin.
Quote:I think Markovich recommended meeting 4...Nbd7 with 5.cxd5 and 6.Bf4 in his old "Hard Chess" column.
The resulting positions with 6. Bf4 bear strong resemblance to those with 6. Bg5, given black will be playing Nh5 soon. The structure takes on an Exchange QGD appearance with Nf3, which is somewhere between += and =.
Not a bad choice to be sure, but not sure if it's critical to black's move order, either.