Against 1.Nf3 d5 2.d4 I'm considering 2...Nd7 as played by Jaffe three or four times in his match against Marshall. Then if play proceeds 3.c4 e6, transposing from the QGD 1.d4 d5 2.c4 e6 3.Nf3 Nd7, we reach a position from 11 of Spielmann's games (according to 365chess), including beating Bogolyubov.
To me there seem to be at least a couple of ideas behind 2...Nd7. Of course, to support ...c5, possibly in such a way as to avoid an isolani. Also, after castling and/or clarification in the center, an eventual ...Nb6, annoyingly exerting control on c4.
To give context, I'm looking for an alternative to 1.Nf3 d5 2.d4 Bf5?! on account of 3.c4. The "QGA and 2...Bf5 against everything else" repertoire I started playing again this year, has served me well however
Interestingly from the initial move order given, 1.Nf3 d5, if White instead tries Keymer's 2.e3, I had already determined I would play .... drum roll please: 2...Nd7