Krishnan Sasikiran slipped to the bottom of the table after losing to Grandmaster Alexei Shirov in the seventh round of the Aerosvit International Grandmasters Chess tournament in Yalta, Ukraine.
Shirov, with three points and in third place, is in contention for the title as other three games ended in draws and the players retained their standings.
On the top board, local hero Sergey Karjakin continued to lead the field with five points after a fine tactical victory over Dutch Grandmaster Loek Van Wely.
Karjakin's compatriot Vassily Ivanchuk scored over Pavel Eljanov to remain within striking distance of the leader.
Sasikiran engaged Shirov in a theoretical battle in the Queen's Indian Defence. The Indian came up with a new idea on the 31st move and forced his opponent into an endgame.
His passed pawn on the seventh rank gave him excellent winning chances but he made a terrible blunder on the 36th move. He suddenly found himself in a hopeless exchange down endgame. Sasikiran fought on for another 15 moves but the outcome was never in doubt.
Karjakin played a solid line against Van Wely's Sicilian Najdorf and the latter appeared to have equalised from the opening. Karjakin got his chance when Van Wely moved his knight away from the kingside and allowed an attack against his king.
Karjakin sacrificed a bishop to open lines against the black king. His attack was irresistible and he won in style by sacrificing a rook and catching his opponent in a mating net in 35 moves.
Ivanchuk faced the Queens Indian defense in his game against Pavel Eljanov and obtained a slight advantage from the opening.
He hung on to his advantage by exchanging queens on the 15th move. Eljanov defended well but Ivanchuk kept trying to complicate matters and provoked some mistakes. This gave him a clear edge and he won a long battle after 53 moves.
Russian Grandmaster Peter Svidler agreed to a quick draw against Liviu Deiter Nisipeanu of Romania. Nisipeanu played a aggressive line against the pirc defense and the players decided not to take chances when a complicated position was reached in 15 moves.
The games -- Jakovenko-Rublevsky and Onishcuk-Dominguez were keenly contested but ended with shared honours.
Results Round 7: Sergey Kajakin (Ukr, 5.0) beat Loek Van Wely (Ned, 3.0); Vassily Ivanchuk (Ukr, 4.5) beat Pavel Eljanov (Rus, 3.0); Aleksey Shirov (Esp, 4.0) beat Krishnan Sasikiran (Ind, 2.5); Alexander Onischuk (USA, 3.5) drew Lenier Dominguez (Cub, 3.5); Sergei Rublevsky (Rus, 3.5) drew Dmitry Jakovenko (Rus, 3.5); Peter Svidler (Rus, 3.5) drew Liviu Deiter Nisipeanu (Rom, 2.5).
The moves: Krishnan Sasikiran - Aleksey Shirov
1. d4 Nf6 2. c4 e6 3. Nf3 b6 4. g3 Ba6 5. b3 Bb4+ 6. Bd2 Be7 7. Bg2 c6 8. Bc3 d5 9. Ne5 Nfd7 10. Nxd7 Nxd7 11. Nd2 O-O 12. O-O Rc8 13. e4 c5 14. exd5 exd5 15. dxc5 dxc4 16. c6 cxb3 17. Re1 b2 18. Bxb2 Nc5 19. Nc4 Bxc4 20. Qg4Bg5 21.Qxc4 Nd3 22. Be5 Nxe1 23. Rxe1 Bf6 24. Bxf6 Qxf6 25. c7 Qd6 26. Rc1 b5 27. Qc2 b4 28. Bb7 g6 29. h4 h5 30. Kf1 a5 31. Qc6 Qxc6 32. Rxc6 a4 33. Ke2 b3 34. axb3 axb3 35. Kd2 Rfe8 36. Ba6 b2 37. Kc2 Re6 38. Rxe6 Rxc7+ 39. Kxb2 fxe6 40. Kb3 Rc1 0-1 - White resigns.