user8573: After
1. e4 c5 2. Nf3 g6 3. d4 cxd4 4. Nxd4 Nc6
Why is the Rossolimo line impossible for white?
[fen ""]
1. e4 c5 2. Nf3 g6 3. d4 cxd4 4. Nxd4 Nc6


user1485: In the Rossolimo proper,
[FEN ""]
[Title "Rossolimo variation"]
[Startply "5"]

1. e4 c5 2. Nf3 Nc6 3. Bb5 g6

white usually holds back pawn to d4 and doubles black pawns with Bxc6, or later builds a center with an eventual c3 followed by d4.
In the Open Sicilian,
[FEN ""]
[Title "Open Sicilian"]
[Startply "9"]

1. e4 c5 2. Nf3 g6 3. d4 cxd4 4. Nxd4 Nc6 5. Bb5?!

none of these plans are available, and 5. Bb5 doesn't make much sense. Besides, the bishop on b5 is tactically vulnerable to a later black Qa5+ or Qb6.

8573: <p>After
1. e4 c5 2. Nf3 g6 3. d4 cxd4 4. Nxd4 Nc6</p>

<p>Why is the Rossolimo line impossible for white?</p>

<pre><code>[fen ""]
1. e4 c5 2. Nf3 g6 3. d4 cxd4 4. Nxd4 Nc6
</code></pre>
 1485: <p>In the Rossolimo proper,</p>

<pre><code>[FEN ""]
[Title "Rossolimo variation"]
[Startply "5"]

1. e4 c5 2. Nf3 Nc6 3. Bb5 g6
</code></pre>

<p>white usually holds back pawn to <code>d4</code> and doubles black pawns with <code>Bxc6</code>, or later builds a center with an eventual <code>c3</code> followed by <code>d4</code>.</p>

<p>In the Open Sicilian,</p>

<pre><code>[FEN ""]
[Title "Open Sicilian"]
[Startply "9"]

1. e4 c5 2. Nf3 g6 3. d4 cxd4 4. Nxd4 Nc6 5. Bb5?!
</code></pre>

<p>none of these plans are available, and <code>5. Bb5</code> doesn't make much sense. Besides, the bishop on <code>b5</code> is tactically vulnerable to a later black <code>Qa5+</code> or <code>Qb6</code>.</p>
