The following game shows what can happen when a player does not know the latest lines in a sharp and complicated opening.

In his prime, Alexei Shirov of Latvia, was one of the most admired players in the world and ranked among the top 5. He has always been one of the most creative players with his entertaining brand of “fire on board” chess. [Editor’s note: The reference is to the two collections of his games that Shirov published which are by the same name.] 

In recent years, Shirov’s results have been less impressive. It isn’t just him growing older and less sharp. One of his biggest woes in recent years has been his opening preparation. It is understandable that he no longer works as hard to keep his repertoire updated, but younger players work on it all the time. This can make a huge difference, particularly when playing Black, as theory can change quickly.   

The following game shows how quickly things can go wrong in a very complicated variation if a player is not up-to-date with the latest ideas. This variation is particularly interesting to me as I saw it develop from the start.

Sethuraman, S.P. vs. Shirov, Alexei
11th Edmonton International | Edmonton | Round 5.1 | 22 Jun 2016 | ECO: D47 | 1-0
1. d4 d5 2. c4 c6 3. Nc3 Nf6 4. e3 e6 5. Nf3 Nbd7 6. Bd3 dxc4 7. Bxc4 b5 8. Bd3 Bb7 9. a3 Bd6 10. O-O O-O 11. Qc2 This is a very interesting position and where our theoretical journey begins. I analyzed this variation a few years ago with my coach, Vladimir Chuchelov, and Anish Giri. After looking at the many 'boring' ways Black can try to equalize, we came up with this ridiculous primitive idea:
11... Rc8!? The plan is to play c5, opening lines for both bishops, which seem to be perfectly positioned to hit the kingside. The pawn on b5 is attacked, but is it really a big deal? A bigger problem is that White can block c5 with
12. b4!? Now c5 can never be played, right? So Rc8 looks like a really dumb move.
12... c5!? !???. When we analyzed this years ago, I marked this move with !! I was particularly proud of this because the computer thinks White has a big advantage in most lines. But if it analyzes longer, it changes its mind quickly enough! I couldn't wait to try this line, and I soon did, against Viktor Laznicka, a grandmaster from the Czech Republic. But he sensed some danger after Rc8 and played Rd1 instead of b4. I got a nice position but unfortunately I messed that up. So the brilliant opening idea didn't quite work out for me. But a few months later, Rustam Kasimdzhanov of Uzbekistan, the former FIDE World Champion, played this line as Black as well. And his opponent, Veselin Topalov of Bulgaria, another former World Champion, didn't quite sense the danger and tried b4. Kasimdzhanov then got to demonstrate the brilliant idea behind c5 and that brought this line to everyone's attention. For a while, Black did great with it, but that was not the end of the story.
13. bxc5 Bxf3! 14. cxd6! An improvement!
14. gxf3 was the obvious move and now Black has the amazing
14... Nxc5! 15. dxc5 Rxc5! The position becomes very complicated, But Black's idea can be summarized as if White tries to defend on the kingside (with f4, for example) then Black wins the knight on c3 by Nd5, Qc7, Rfc8, etc. And then the equal material is enough to draw the game. If White tries to save the knight with
16. Bb2 or Qb3, etc., then
16... Bxh2+! 17. Kxh2 Rh5+! 18. Kg3 Rg5+! 19. Kh4 Rh5+ 20. Kg3 Rg5+ And Black can force perpetual check.  )
14... Nd5 15. gxf3 Qg5+ 16. Kh1 Qh5 17. Be2! The crucial idea that changed everything. The computers suggestion is Bxh7 and it assesses White having a big advantage. But Black is ok in that line. Now, the computer thinks Black is fine, but after
17... Nxc3 18. Rg1 Things are surprisingly hard for Black. He still needs to try to win the pawn on d6 and White is the one who has the initiative. The game has completely turned around again. It shows how fickle the computer assessments are. This new idea was eventually found, and played for the first time by Surya Ganguly, an Indian grandmaster, who won more than one game in this variation. Since then, many other players have played the same moves and scored very well. Shirov obviously did not know this and was under the impression that this was fine for Black. He must have analyzed this line in some detail after Kasimdzhanov's win over Topalov. Over the board, he soon realizes that his analysis is out of date and he is unable to put up much resistance.
18... Nf6 19. Bb2 Na4 Nxe2 was better, but things were definitely not easy and the bishop on b2 is very dangerous. Shirov tries to improvise, but how can he deal with the pawn on d6?
20. Qd2 Rfd8
20... Nxb2 21. Qxb2 Rfd8 22. e4  )
21. e4 Rxd6 The idea is that the queen might be misplaced on d2 and he hopes to meet e5 by Qxe5. But
22. e5! still wins because Qxe5 loses to Qh6! and Black just loses a piece.

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Parimarjan Negi is an Indian grandmaster who is the second-youngest ever to earn the title (at 13 years 4 months and 22 days). Ranked No. 90 in the world, he just finished his sophomore year at Stanford University.