I partipated in a tournament last weekend. My 5th round opponent knew I played the Blackmar Diemer and was prepared for it, since I had played a Blackmar Diemer against him a year ago or so.
So I had the bad idea of playimng something else...
1.d4 d5 2.c4
No mother what the grandmasters say : bad choice - 2.e4 is far better/
3.Nf3 Nf6 4.Nc3 dxc4 5.e4 b5 6.Qc2
My knowledge of theory had ended here. Better was 6.e5, entering the Geller gambit.
Cant be bad, can it ?
This cant be right !!!
8.axb5 cxb5 9.Nxb5 (diagram)
I won my gambit pawn back and my position is far better !!!
But my opponent got me into a known Slav ambush.
9...axb5!!! 10.Rxa8 Bb7 11.Ra1
I started to feel unconfortable, especially since my opponent was smiling all the time
And here I knew I was in really deep shit
Desperately trying to get my king into safety
Black develops quickly
13.Bd2 Nxd2 14.Nxd2 Qg5 (diagram)
Here I decided to resign. My king has no place to go as castling queenside is not possible anymore.
What a nice trap !!
Lessons learned - stick to the Blackmar Diemer and dont mess with Slav gambits.