user10456: [Title "White to move"]
[FEN "1r3rk1/1p4bp/p2p1q2/2pPn1p1/B1PnRp2/PPN2P1P/2QB2P1/3R2K1 w - - 5 27"]

This is a diagram from the game between Del Rey, Diego and Efimenko, Zahar on the Zalakaros Chess Festival after 26...Nd4. White answered with 27.Rxd4. I don't understand why white needed to sacrifice his rook for the knight in this position.

user7297: Well, he has to because there is no other option. The black Knight threatens to capture the white Queen, but also a 'sacrifice' on f3 which will eventually win the white Knight on c3.
[Title "White to move"]
[FEN "1r3rk1/1p4bp/p2p1q2/2pPn1p1/B1PnRp2/PPN2P1P/2QB2P1/3R2K1 w - - 5 27"]

1. Qb2? Ndxf3+ 2. gxf3 Nexf3+ 3. Kg2 Nxd2 4. Qxd2 Qxc3

This might not even be the best variation for Black. In any case, even after the sacrifice, White is still lost.

10456: <pre><code>[Title "White to move"]
[FEN "1r3rk1/1p4bp/p2p1q2/2pPn1p1/B1PnRp2/PPN2P1P/2QB2P1/3R2K1 w - - 5 27"]
</code></pre>

<p>This is a diagram from the game between Del Rey, Diego and Efimenko, Zahar on the Zalakaros Chess Festival after 26...Nd4. White answered with 27.Rxd4. I don't understand why white needed to sacrifice his rook for the knight in this position.</p>
 7297: <p>Well, he has to because there is no other option. The black Knight threatens to capture the white Queen, but also a 'sacrifice' on f3 which will eventually win the white Knight on c3.</p>

<pre><code>[Title "White to move"]
[FEN "1r3rk1/1p4bp/p2p1q2/2pPn1p1/B1PnRp2/PPN2P1P/2QB2P1/3R2K1 w - - 5 27"]

1. Qb2? Ndxf3+ 2. gxf3 Nexf3+ 3. Kg2 Nxd2 4. Qxd2 Qxc3
</code></pre>

<p>This might not even be the best variation for Black. In any case, even after the sacrifice, White is still lost.</p>
