He was the only one to win a game on Tuesday and he now has a half-point lead on his nearest rivals in the Sinquefield Cup.

There could easily have been a few decisive games in Round 5 of the Sinquefield Cup. But in the end, only Veselin Topalov of Bulgaria was able to take advantage of the chances that were offered him. With his victory, he is now the sole leader with 3.5 points. Three other players, Levon Aronian of Armenia, Wesley So of the United States and Viswanathan Anand of India, trail Topalov by half a point. 

Topalov’s victory was over Ding Liren of China, who had Black and employed the Zaitsev Variation in the Spanish opening. Ding has started playing this variation only recently and he didn’t seem at ease in the opening after Topalov chose a somewhat unusual sideline. Ding sacrificed a pawn to try to gain some counterplay but he never seemed to have quite enough compensation. Once he was down and in trouble, he fought back creatively and, combined with some inaccuracies by Topalov, almost saved it:

Topalov, V. vs. Ding Liren
4th Sinquefield Cup 2016 | Saint Louis USA | Round 5 | 09 Aug 2016 | ECO: C92 | 1-0
1. e4 e5 2. Nf3 Nc6 3. Bb5 a6 4. Ba4 Nf6 5. O-O Be7 6. Re1 b5 7. Bb3 d6 8. c3 O-O 9. h3 Re8 10. d4 Bb7 11. Nbd2 Bf8 12. a3 h6 13. Bc2 Nb8 14. b3 This is not the most uncommon continuation for White in this opening, but it is understandable that Ding probably never looked into too carefully as it does not seem to be particularly dangerous for Black.
14... Nbd7 15. Bb2 Rc8? Black prepares a typical pawn sacrifice to gain counterplay, but it usually occurs in games arising out of the Breyer Variation, not the Zaitsev. Dings idea is not a fatal mistake, but clearly it is the wrong plan.
16. a4 b4 A natural continuation after Rc8, but it is really a mystery to me what Black was hoping to achieve. I guess Ding just felt uncomfortable with the typical but passive positions after c6.
17. cxb4 exd4 18. Bxd4 c5 19. bxc5 Nxc5 20. Qb1 White is up a pawn up and Black has no real compensation.
20... a5 21. b4 axb4 22. Qxb4 Ba8 White had many ways to preserve his advantage. The next moves weren't particularly interesting:
23. a5 d5 24. Bxf6 Qxf6 25. e5 Qa6 26. Qg4 Ne6 27. Bf5 Rc5 28. Bxe6 Rxe6 29. Nb3 Rc4 30. Nfd4 Bb7 31. Qf5 Re7 32. e6 Bc8! Black's position seems to be on the verge of collapse, but giving up a second pawn to gain activity allows him to keep fighting.
33. exf7+ Rxf7 34. Qxd5 Bb7 35. Qe6 Rb4!? In an endgame the two bishops can cause White some headaches. Both players were probably also in time pressure as they approached the first time control, so Ill hold my comments here:
36. Re3 Qa8 37. Rc1 Bd5 38. Rc8 Bxe6 39. Rxa8 Bc4! 40. Rc8 Kh7 Again, the two bishops are a nuisance. Topalov struggles to create much play in the next few moves while Ding defends excellently:
41. Rc3 Ba6 42. Rd8 Ra4 43. Ne6 Bb4 44. Rc6 Bb5 45. Rc1 Ra2 46. f3 Ba4 47. Nbd4 Bxa5 48. Ra8 Bb6 49. Kh1 Bb3 50. Rb8 Bxe6 51. Rxb6 Bf5 52. Rd6 Finally things have calmed down. The endgame should be a long, hard defense for Black because of the knight vs bishop balance, but it is definitely not easy to win. I would have expected White to try to slowly make progress, but Topalov goes for a knockout by aiming to trying to create mating nets for the Black king.
52... Bg6 53. Rd8 Bf5 54. Rd6 Bg6 55. Rc8 Rb7 Seeking counterplay.
56. Rdd8 Bd3! Black wants to play Bf1, but that turns out to be a mistake!
57. Ne6 Bf1?! it was really hard for Black to calculate the consequences of this move, so the decision is understandable.
57... Bf5! was more logical as exchanging the bishop for the knight would lead to a drawn rook-and-pawn ending and it would not be easy for White to avoid. Ding did not anticipate Whites plan of attack.
58. Nf8+ Kg8 the king is safe  )

Topalov fumbled a bit at this point, but Ding missed a way to draw the game. In the end, Topalov wrapped it up with a study-like mating net:

Topalov, V. vs. Ding Liren
4th Sinquefield Cup 2016 | Saint Louis USA | Round 5 | 09 Aug 2016 | ECO: C93 | 1-0
58. Nf8+? Probably trying to gain time, but this allows Black a chance to draw.
58... Kg8 59. Ng6+ Kh7
59... Kf7 60. Nf4 Bxg2+! is probably what Ding missed.
61. Nxg2 Rb1+ 62. Kh2 Rbb2 and it is a draw.  )
60. Nf8+ Kg8 61. Ne6+ Kh7? Ding completely misses Whites threats to thehis king. He probably thought it was a draw and so didn't need to be so precise.
61... Kf7! once again was a draw
62. Nf4 Bxg2+! 63. Nxg2 Rb1+ 64. Kh2 Rbb2!  )
62. Rh8+ Kg6 63. Nf4+ Kg5 64. Rhf8! Rbb2
64... Bxg2+ seems like it should still be a draw but now White has
65. Kh2!! Bxf3+ 66. Kg3 and Blacks king is in a mating net!
66... Be4 67. h4#  )
65. Rc7! g6 66. g3 And h4 mate can't be avoided

Fabiano Caruana of the United States was probably disappointed after the round as he a chance to join Topalov in the winner’s circle, but he let Maxime Vachier Lagrave of France off the hook. Caruana employed an unusual opening setup and in the middlegame, he slowly improved his position and put Vachier-Lagrave under pressure:

Caruana, F. vs. Vachier Lagrave, M.
4th Sinquefield Cup 2016 | Saint Louis USA | Round 5 | 09 Aug 2016 | ECO: B54 | 1/2-1/2
Nac5 Black seemed to be doing fine, but...
20. Kf1! the advantage of this move over castling is that after fxg3, Whites rook would be perfectly placed. And fxg3 is a move that Black wants to play to create space for his pieces.
20... Qe8 21. Re1 Another nice idea. Caruana is preparing a devilish response against e4
21... e4
21... Qh5 22. Kg2  )
22. Bxc5 Nxc5 23. Nxe4! Nxe4 24. Bd3! fxg3 25. Bxe4 Qh5? I am surprised that Vachier-Lagrave didn't try
25... g2+! 26. Kxg2 Qh5  )
26. Kg2! gxh2 27. Rxh2 Bh4 28. Bxh7+! Kh8
28... Qxh7 29. Qxh7+ Kxh7 30. Rxh4+ Kg8 31. Re7 is too unpleasant.  )
29. Be4 Black's position looks as if it is on the verge of collapse, but Vachier-Lagrave finds a very stubborn defensive setup to block up the kingside.
29... Rf4! 30. Kh1 Qe5 31. Rg1
31. c5! was the best way to proceed. Opening the queenside would have been unpleasant for Black because his bishop is permanently stuck on the kingside. And with more open files and diagonals, the Black King would be very uncomfortable.  )
31... g5! Black's defensive setup on the kingside is surprisingly robust. For now, everything is blocked.

Vachier-Lagrave’s defense, particularly the setup with g5(!) was very commendable, but it probably shouldn’t have been enough to save the game. But Caruana tried to play a bit too technically by converting to an endgame with rooks and opposite-colored bishops in which White would have a clear edge. The problem was that endgames with only opposite-color bishops are often drawn and Caruana missed Vachier-Lagrave’s nice defensive resource which forced a trade of rooks:

Caruana, F. vs. Vachier Lagrave, M.
4th Sinquefield Cup 2016 | Saint Louis USA | Round 5 | 09 Aug 2016 | ECO: B56 | 1/2-1/2
32. Qc3 I can understand why this move looks tempting. After bxc3, White can double his rooks on the b-file, which looks dangerous for Black. But I think Caruana overlooked a really nice defensive trick that Vachier-Lagrave finds.
32... Qxc3 33. bxc3 Kg7 34. Rb1 Rf7 35. Rb6 the pressure on the pawn on d6 is the key. If Black defends passively with Rd8-Rd7, then at some point White will play c5 and create a passed d-pawn, building the pressure on Black.
35. Rhb2 Rc8!  )
35... Ra6! 36. Rhb2 Rxb6 37. Rxb6 Bf2! The defensive resource that Caruana missed.
38. Rxd6 Rf6! White can't avoid the rook exchange and the opposite-colored bishop endgame is a draw.
39. Rd8 Rf8 40. Rd6 Rf6 41. Rd8 Rf8 42. Rxf8 Kxf8 43. d6 Bc5 44. d7 Ke7 45. Bf5 Be3 46. Kg2 Bd2 47. Kf2

Anish Giri of the Netherlands had a short draw against Aronian after playing two marathon draws in the previous two rounds, but the game had a very interesting middlegame. In a fairly typical position, Giri played f4, which was fascinating and double-edged. His follow-up was too ambitious and almost gave Aronian a huge advantage:

Giri, A. vs. Aronian, L.
4th Sinquefield Cup 2016 | Saint Louis USA | Round 5 | 09 Aug 2016 | ECO: A29 | 1/2-1/2
c6 14. f4!? It is very interesting how White generates pressure in this position. If he can play f5 and f6 then Black's kingside starts looking dodgy.
14... f5 15. e4 Rf7 16. Bh3 Very ambitious, but it doesn't seem sound to move the perfectly placed bishop on g2. White's idea is that after the light-squared bishop exchange, Black's position looks more vulnerable, and White can develop quickly with moves like Qb3, Rd1, etc. But White had a clear edge if he had continued more traditionally, so this was a strange plan coming from a player like Giri who is very strategically sound player. Aronian finds a very good way to create counterplay. The key idea is that the rook on f7 can swing over to d7 to create pressure along the d-file.
16. exf5 Bxf5 17. Ne4  )
16... Bb4! 17. Bxf5 Bxf5 18. exf5 Nc4! and Rd7 will be next
18... Rd7 19. Qb3+  )
18... Rxf5 19. Qb3+ Kh8 20. Rbd1  )
19. Qd3
19. a3 Rd7!  )
19... c5 settling for equality.
19... b5 was more ambitious, but the position would have been crazy  )
20. Qxc4 Qxd4+ 21. Qxd4 cxd4 22. Ne4 Re8 23. a3 Rxe4 24. axb4 axb4 25. Rbe1 Rxe1 26. Rxe1 Rxf5 27. Rd1 Rc5 28. Rxd4 Rc1+ 29. Kg2 Rc2+ 30. Kh3

The game between Peter Svidler of Russia and Hikaru Nakamura of the United States was also very interesting. Svidler achieved a slight edge, which he nursed for a long time, but it wasn’t clear how to take advantage of it. Nakamura fought back and managed to almost turn the tables. The game ended with some crazy complications that seem impossible to assess, but were entertaining to watch:

Svidler, P. vs. Nakamura, Hi
4th Sinquefield Cup 2016 | Saint Louis USA | Round 5 | 09 Aug 2016 | ECO: E63 | 1/2-1/2
Rb6 24. b5 With hindsight
24. Nc4! Rb7 25. b5 would have been a lot more difficult for Black as now c6 is not possible. Black's position would be a little worse, though nothing disastrous.  )
24... c6! 25. Nc4 White could have kept a slightly better position in some other ways but after the pawn exchange his advantage disappears.
25... Rxb5! 26. Rxb5
26. Bxd6 is the criticial line. Now Black would have some nice possibilities:
26... Rxb1 27. Qxb1 Bxd4! if Bxf8, White is ahead in material, but then after Qf8-c5-Nf4, etc., Black would completely control the dark squares!
28. Rd1 c5! 29. Bxc5 Bxc5 30. Rxd8 Rxd8 and the compensation is probably enough for a draw.  )
26... cxb5 27. Nxd6 b4 The position begins to look tricky for White as well.
28. e5 Nc6 29. Bc4 Qb6 30. d5! White is just in time to create complications, muddying the situation.
30... Bxe5 31. Bxe5 Ncxe5 32. dxe6 fxe6 33. Bxe6+ Kh8 34. Bf5 I have no idea how to assess this position. The computer's evaluation that chances are equal isn't very helpful.
34... b3!? the next few moves were among the best according to the engine. There seem many other interesting moves as well, but the position is very hard to play for both players.
35. Qd5 b2 36. Rb1 Qc7 37. Bxg6 Qc1+ 38. Kg2 Nxg6 39. Qd4+ Kg8 40. Qd5+ Kh8 41. Qd4+ Kg8

The last game of the day between Anand and So was comparatively tamer. The key here was So’s creative play in the opening, which eventually led to a double pawn sacrifice for long-term compensation:

Anand, V. vs. So, W.
4th Sinquefield Cup 2016 | Saint Louis USA | Round 5 | 09 Aug 2016 | ECO: C50 | 1/2-1/2
16. Na3 b4! One pawn sacrifice isn't enough of course!
17. cxb4 Accepting the pawn makes sense. But now White's pawn structure is broken and Black's two bishops and better positioned pieces provide him adequate compensation.
17. Nc2 bxc3 18. bxc3 Ng6 19. Nxg6 hxg6  )
17... Qd5 The game could have become more exciting, but Anand accepts that Black has compensation for his material deficit and decides to force exchanges in order to reach an equal position.
18. Nec4
18. d4 Rd8 19. Nf3 Ng6  )
18... Bxd3 19. Rxe7 Bxc4 20. Qxd5 Bxd5 White is still up a pawn, but it isn't very impressive. And White's pieces are too passive to cause Black any problems.
21. Rd7 Bc6 22. Rd1 Ba4 23. Rd3 Bc7 24. b3 Bc6 25. f3 Rd8 26. Rxd8+ Bxd8 27. b5 Bd7 28. Kf2 Be7 29. Ke2 Bxa3 30. Bxa3 Bxb5+

Despite the many draws in the tournament, the games continue to be very exciting. Wednesday is a rest day and then the tournament begins its home-stretch on Thursday with Round 6.

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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. He can be found on Twitter at @parimarjan.