Hi Hamworld
Cliche's have the place but are often over used....
(Hence the term 'cliche' you greenpawn dimwit.......The Duck)
.....they get tossed about all over the place and very often for the wrong reason.
Here it was forced (I know you like Bd3 but stay with me.).
The time to start pointing out Na3's as
potential game losing errors is
when they are not forced and moved to a3 for no other reason than the fact
it was White's turn to move.
Regarding the actual game.
Everyone is running around expressing great concern for an unmoved a1 Rook.
I know I'm out of touch with what's happening in the Chess world but the
last time I looked the object of the game was to checkmate the King.
After this I'll Google the FIDE site to see if they have changed it to capturing the a1 Rook.
That Knight will take 4 moves precious opening moves to nick an undeveloped,
unmoved scaffy Rook which will have no significant role to play till I decide to
open the centre (I may not want to).
Saving the useless Rook commits me to a strategy. I refuse to be blackmailed
into a strategy. (not much choice after 1.d4 and 2.f4 - yuk!)
Meanwhile White has holes in his position (1.d4 and 2.f4 - yuk!) which at the
moment can be only exploited by Knights....Not Rooks.
His agile Knight is worth more than a lumbering Rook.
So sac the Rook....and a Knight...and a Bishop....
1. d4 d5 2. f4 Bf5 3. Nf3 Nc6 4. e3 Nb4 5. Ne5 Nxc2+ 6. Kf2 Nxa1 {There goes the Rook. Has the game stopped. No. Good. FIDE have not changed the rules, I have no need to Google them.} 7. g4 Bxb1 {Black is solving the problem of White's undeveloped pieces by removing them from the board.} 8. Ba6 {Now rather than tie down the Rook to defensive duties with 8....Rb8. Black elects to saddle himself with double pawns knowing the open b-file will be off benefit to him. Here Black uses the advantage of the open file to counter the disadvantage of double pawns.} 8... bxa6 9. Qa4+ {And White mates Black in two moves.}