user32939: I was analyzing a game and found that the engine gives -3.42 after 1. Rb1 and +2.72 after the subsequent 1. ...Nc2. Is Nc2 really such a bad move? For comparison, 1. ... Nd5? results in almost the same score (+2.62) but with loss of material for black. On the other hand Nc2 allows white to connect rooks and gain a tempo with Kd2, but is it that strong?
[fen "r3k2r/ppp2ppb/7p/4p2P/1nP3P1/3P1N2/P3BP2/R3K2R w KQkq - 0 19"]

1. Rb1 Nc2+?! 2. Kd2 Nd4 3. Nxd4 exd4 4. Rxb7


user8300: ...Nc2?? is indeed a terrible move here.
Doing a simple material count we see that black is a pawn up, and if we start looking for checks and captures in the position we immediately see that black can just take another pawn on d3 with check! This is why black is winning in the original position: black is simply going to pick up a bunch of pawns and white will not be able to capture enough pawns to counterbalance this. (quick exercise: why can't white capture the pawn on b7 after the sequence 1...Nxd3+, 2.Bxd3, Bxd3? EDIT: seems like I was a bit hasty in my analysis when I posted this; as indicated in the comments white should actually play 3.Rxb7 here, as I missed that after 3...Be4 with a fork white can defend with 4.Rb3)
But if black doesn't pick up the free pawns available, then there is absolutely nothing that speaks in favour of black's position. And this is part of the reason why ...Nc2 is such a terrible move. Not only does it ignore the opportunity to take free material and win, it also gives away free material to white!
But this is not the end of black's troubles after playing the outright blunder ...Nc2+?? After white plays Kd2 in response, the black knight is forced to move, and this gives white the chance to invade on the 7th rank with a rook. In general, this tends to be very dangerous to allow, and this position is no exception. The rook on b7 will wreak havoc on black's position, attacking weak pawns and disturbing coordination. And what will black have to show for this? The answer is nothing.
It might seem strange at first glance that ...Nc2+?? is evaluated as basically equally terrible as ...Nd5?? But while ...Nc2+?? doesn't lose an entire piece, it does give white material for free while also giving white's pieces excellent squares to go to. At the same time it manages to destroy black's pawn structure by giving away a vital pawn on b7. In comparison, ...Nd5?? only loses material (although a decisive amount of it).
So, in conclusion: no, ...Nc2+ is not a dubious move. It's an outright blunder. The reason for this is two-fold.

It ignores the opportunity to just take a free pawn! (in fact, in the given position any move other than taking on d3 can be seen as a severe blunder, as it fails to do the basic tactic check one should do before any move)
It gives away free material to white while at the same time helping white's position get stronger.


32939: <p>I was analyzing a game and found that the engine gives -3.42 after <code>1. Rb1</code> and +2.72 after the subsequent <code>1. ...Nc2</code>. Is <code>Nc2</code> really such a bad move? For comparison, <code>1. ... Nd5?</code> results in almost the same score (+2.62) but with loss of material for black. On the other hand <code>Nc2</code> allows white to connect rooks and gain a tempo with <code>Kd2</code>, but is it <em>that</em> strong?</p>
<pre><code>[fen &quot;r3k2r/ppp2ppb/7p/4p2P/1nP3P1/3P1N2/P3BP2/R3K2R w KQkq - 0 19&quot;]

1. Rb1 Nc2+?! 2. Kd2 Nd4 3. Nxd4 exd4 4. Rxb7
</code></pre>
 8300: <p>...Nc2?? is indeed a terrible move here.</p>
<p>Doing a simple material count we see that black is a pawn up, and if we start looking for checks and captures in the position we immediately see that black can just take another pawn on d3 with check! This is why black is winning in the original position: black is simply going to pick up a bunch of pawns and white will not be able to capture enough pawns to counterbalance this. (quick exercise: why can't white capture the pawn on b7 after the sequence 1...Nxd3+, 2.Bxd3, Bxd3? <strong>EDIT: seems like I was a bit hasty in my analysis when I posted this; as indicated in the comments white should actually play 3.Rxb7 here, as I missed that after 3...Be4 with a fork white can defend with 4.Rb3</strong>)</p>
<p>But if black doesn't pick up the free pawns available, then there is absolutely nothing that speaks in favour of black's position. And this is part of the reason why ...Nc2 is such a terrible move. Not only does it ignore the opportunity to take free material and win, it also gives away free material to white!</p>
<p>But this is not the end of black's troubles after playing the outright blunder ...Nc2+?? After white plays Kd2 in response, the black knight is forced to move, and this gives white the chance to invade on the 7th rank with a rook. In general, this tends to be very dangerous to allow, and this position is no exception. The rook on b7 will wreak havoc on black's position, attacking weak pawns and disturbing coordination. And what will black have to show for this? The answer is nothing.</p>
<p>It might seem strange at first glance that ...Nc2+?? is evaluated as basically equally terrible as ...Nd5?? But while ...Nc2+?? doesn't lose an entire piece, it does give white material for free while also giving white's pieces excellent squares to go to. At the same time it manages to destroy black's pawn structure by giving away a vital pawn on b7. In comparison, ...Nd5?? only loses material (although a decisive amount of it).</p>
<p>So, in conclusion: no, ...Nc2+ is not a dubious move. It's an outright blunder. The reason for this is two-fold.</p>
<ol>
<li>It ignores the opportunity to just take a free pawn! (in fact, in the given position any move other than taking on d3 can be seen as a severe blunder, as it fails to do the basic tactic check one should do before any move)</li>
<li>It gives away free material to white while at the same time helping white's position get stronger.</li>
</ol>
