Five-time world champion Viswanathan Anand's hunt for an elusive win continued as he was held to yet another draw by Shakhriyar Mamedyarov of Azerbaijan in the sixth round of the Altibox Norway Chess tournament, Stavanger, Norway.
American Wesley So threw the tournament open by scoring a crushing victory over Magnus Carlsen of Norway.
With his sixth draw in as many games, Anand took his tally to 2.5 points in all as the game against Ding Liren, who withdrew due to injury, was declared null and void.
The Indian ace still has three more games to play in the strongest tournament of the year and technically he is just a half point behind Carlsen, who was struck by Wesley for the first time ever in a classical game.
This was not only Weslay's first victory, it was also the first loss that Carlsen suffered this year after a streak of 37 undefeated classical games.
The reigning world champion can still take some solace from the fact that he is still tied for first spot with Wesley but the fact remains that Wesley has three games remaining while Carlsen has just two more to play in the nine-player tournament.
For Anand, it was a day that did not start well. Mamedyarov's fianchetto variation in the Ruy Lopez was something the Indian probably did not expect and after a sedate opening, the Azerbaijani thought he had a decent position.
Anand probably agreed with this view too as pieces changed hands at regular intervals and the payers arrived at a drawn rook and pawns endgame to sign peace.
Wesley went for the exchange variation in the Slav defense and found that Carlsen was not quite prepared to tackle the fine prints. The middle game had some advantage for Wesley that he nurtured after sacrificing a pawn temporarily on the queen side.
The American then won two pawns in tandem before launching a decisive attack on the king side.
"This was not fun. Well played by Wesley. Credit goes to him, because he played a great game," was how Carlsen summed up the game.
Carlsen thus remained on 3.5 points out of a possible six games and still has two games to go. Wesley, Levon Aronian of Armenia now follow the Norwegian on three points each but Wesley has played just five games and has an extra game in hand.
Anand is now on 2.5 points sharing the fourth spot with American duo of Hikaru Nakamura and Fabiano Caruana, Sergey Karjakin of Russia and Mamedyarov. Maxime Vachier-Lagrave of France is at the bottom with two points in all.
Results after Round 6: Vishwanathan Anand (IND, 2.5/5) drew with Shakhriyar Mamedyarov (AZE, 2.5/6); Wesley So (USA, 3/5) beat Magnus Carlsen (NOR, 3.5/6); Hikaru Nakamura (USA, 2.5/5) drew with Maxime Vachier-Lagrave (FRA, 2/5); Levon Aronian (ARM, 3/6) drew with Fabiano Caruana (USA, 2.5/5).