Playing the Modern against the Austrian is usually generating pretty sharp games, but for both sides! It's developing a fight in which the stronger (and maybe better prepared) player should take home the full point.
To some degree, White cannot rest on his big center and normal piece development, since anytime Black might strike back in the appropiate moment.
As you pointed out, if White wants to limit the risk by spending a full tmepo on the poor a3, Black immediately should be fine.

As in a lot of different Modern lines, Black should retain flexibily in order to survive White's critical replies and must be prepared for all kind of ideas (some of them are solid, some are critical), for example after

1.e4 g6 2.Bg7 d4 3.Nc3 d6 4.f4 a6 5.Nf3 b5 6.Bd3 Nd7 Black needs to know, what to do after 7.e5 c5 8.Be4/8.Ng5/8.e6 as well as 7.Be3 Bb7 8.e5/8.0-0/Qe2 just to name a few.

In my mind, the Modern is hard to learn, but it can pay off not only in terms of good preperation but in chess understanding in general.

Michael Ayton wrote on 06/29/17 at 11:16:04:


Well, that's of course a perfectly sound option, but playing the Modern against the Austrian should be fun as well! 

JhF wrote on 05/13/10 at 17:17:27:


Quite an interesting and sharp line, which is covered in-depth in The Modern Tiger.
First of all, Black has an alternative along the way in 9...Nh6 intending 10.exd6 0-0!? with unclear play. In the position after 9...cxd4 and finally 12.Kh1, Tiger (p.33) briefly discusses 12...b4 (appearently a specialty by V. Nithander), but after 13.Na4! Qc7 (13...Qb5 14.c4!) 14. Nxb8 Qxb8 15.fxe5! (the engine likes this move best) Black's compensation seems dubious.

I remember a game played by Carlsen (Black) last year vs. Wei,Yi, which continued differently (but nevertheless just as exciting) with 8.Be3 Bb7 9.Be4 Bxe4 10.Nxe4 Nh6 11.dxc5 dxe5 and Carlsen went on to win.
I don't know about the current evaluation of this line (and the Modern Austrian in general!), but would be great to see more of these high-level examples! 

For those of us who are not super familiar, can you give the moves to get to the above position?  Thanks.