Mr. Patxi Mutiloa, Director of Sports of the Basque Government made the first move of the 4th round
In the game between Shirov and Karjakin, Shirov had the opportunity to overtake his irregular start facing Karjakin with white pieces. After playing the first moves of the Zaitsev variation of the Spanish Opening, black gave a pawn for initiative based on a strong pawn on white's 3rd row. In the critical moment, Sergei thought a lot about his options increasing the pressure on his oponent's king, but after not finding anything, played a forced variation that lead to a perpetual-check draw.
In the decisive game the two leaders faced each other, Aronian vs. Grischuk. They played the Chevanenko variation of the Slav, where the black player advanced his queenside pawns quickly. In the 10th move, Aronian gave a piece for three pawns playing a novelty. After some moves, they exchanged a lot of pieces which lead to a favourable position for white, with many options to attack black's king. Grischuk was very short on time, he reached the 40th move control with just 12 seconds on his clock, and that didn't help him to find the best defense for his position. After regrouping his pieces, Aronian showed that his initiative against black's king was unstoppable, and he won his game and got 3 more points.