user10182: Yesterday Anish Giri played the scotch opening at the Tata Steel Tournament with the strange looking move(to me) 5.Nf3.
[fen "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1"]

1.e4 e5 2.Nf3 Nc6 3.d4 exd4 4.Nxd4 Qf6 5.Nf3

What is the idea/plan behind this move after retreating the knight immediately.
From my point of view i would assume the knight is better placed on d4 than on f3.
Can white even hope to have an opening advantage after this move?

user12282: They're playing on the extremely high level and opening preparation is amongst the things they invest the most of their time so they're always searching for the new ways to spice the game up and thus increase their chances for the victory.I don't think there's a deep idea behind Nf3.

user4588: After 4....Qf6, both 5.Be3 and 5.Nxc6 are likely to transpose to 4....Bc5: 5.Be3 Bc5 and 5.Nxc6 Bc5. Instead, 5.Nf3 seems to be an interesting alternative, with chances to obtain an advantage. It worked quite well for Giri, as he was pressing the entire game.
After 5.Nf3, black should probably be able to equalize. Andreikin played the precise 5....Bb4+ and the game continued 6.c3 Bc5 7.Be2 d6 8.0-0. Black followed up with the logical 8....Nge7, but ended up in a worse position after 9.b4 Bb6 10.Bg5. Note that 9....Nxb4 or 9....Bxb4 doesn't work because of 10.Bg5. Instead, 8....a6 and 8....Qe7 (to play Nf6) are probably better alternatives, after which black should be able to keep the balance.
Actually, one can also wonder why black would give white the opportunity of 5.Nf3 by playing 4....Qf6 instead of 4....Bc5.
Two possible reasons are: 

After 4....Qf6 5.Nxc6, black wants to play 5....dxc6, instead of 5....Bc5. This way, he can still chose between Bb4, Bc5 or Bd6.
Black doesn't like the position after 4....Bc5 5.Nb3 Bb6 6.Nc3 Nf6



      [StartPly "7"]

      [FEN ""]
      1.e4 e5 2.Nf3 Nc6 3.d4 exd4 4.Nxd4 Qf6 (4...Bc5 5.Nb3 (5.Be3 Qf6)(5.Nxc6 Qf6) Bb6 6.Nc3 Nf6) 5.Nf3 (5.Be3 Bc5)(5.Nxc6 dxc6 (5...Bc5)) Bb4+ 6.c3 Bc5 7.Be2 d6 8.O-O Nge7 (8...a6)(8...Qe7) 9.b4 Bb6 (9...Nxb4 10.Bg5)(9...Bxb4 10.Bg5) 10.Bg5




10182: <p>Yesterday Anish Giri played the scotch opening at the Tata Steel Tournament with the strange looking move(to me) 5.Nf3.</p>

<pre><code>[fen "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1"]

1.e4 e5 2.Nf3 Nc6 3.d4 exd4 4.Nxd4 Qf6 5.Nf3
</code></pre>

<p>What is the idea/plan behind this move after retreating the knight immediately.
From my point of view i would assume the knight is better placed on d4 than on f3.</p>

<p>Can white even hope to have an opening advantage after this move?</p>
 12282: <p>They're playing on the extremely high level and opening preparation is amongst the things they invest the most of their time so they're always searching for the new ways to spice the game up and thus increase their chances for the victory.I don't think there's a deep idea behind Nf3.</p>
 4588: <p>After 4....Qf6, both 5.Be3 and 5.Nxc6 are likely to transpose to 4....Bc5: 5.Be3 Bc5 and 5.Nxc6 Bc5. Instead, 5.Nf3 seems to be an interesting alternative, with chances to obtain an advantage. It worked quite well for Giri, as he was pressing the entire game.</p>

<p>After 5.Nf3, black should probably be able to equalize. Andreikin played the precise 5....Bb4+ and the game continued 6.c3 Bc5 7.Be2 d6 8.0-0. Black followed up with the logical 8....Nge7, but ended up in a worse position after 9.b4 Bb6 10.Bg5. Note that 9....Nxb4 or 9....Bxb4 doesn't work because of 10.Bg5. Instead, 8....a6 and 8....Qe7 (to play Nf6) are probably better alternatives, after which black should be able to keep the balance.</p>

<p>Actually, one can also wonder why black would give white the opportunity of 5.Nf3 by playing 4....Qf6 instead of 4....Bc5.
Two possible reasons are: </p>

<ul>
<li>After 4....Qf6 5.Nxc6, black wants to play 5....dxc6, instead of 5....Bc5. This way, he can still chose between Bb4, Bc5 or Bd6.</li>
<li>Black doesn't like the position after 4....Bc5 5.Nb3 Bb6 6.Nc3 Nf6</li>
</ul>

<pre>
<code>
      [StartPly "7"]

      [FEN ""]
      1.e4 e5 2.Nf3 Nc6 3.d4 exd4 4.Nxd4 Qf6 (4...Bc5 5.Nb3 (5.Be3 Qf6)(5.Nxc6 Qf6) Bb6 6.Nc3 Nf6) 5.Nf3 (5.Be3 Bc5)(5.Nxc6 dxc6 (5...Bc5)) Bb4+ 6.c3 Bc5 7.Be2 d6 8.O-O Nge7 (8...a6)(8...Qe7) 9.b4 Bb6 (9...Nxb4 10.Bg5)(9...Bxb4 10.Bg5) 10.Bg5

</code>
</pre>
