There were only two decisive games today, but there could easily have been two more. One of the winners was Fabiano Caruana, who bounced back from yesterday's loss with an impressive win over Sergey Karjakin from the white side of an Open Catalan. Karjakin never managed to achieve the liberating ...c5 advance, and was gradually ground down. The other win was Penteala Harikrishna's long victory over Leinier Dominguez. Dominguez could have liquidated to an easy draw with 26...Rxb1 27.Bxb1 b5 or 29...b5. Instead, 27...b6, 29...Rb8 and 32...a5 created a static structure that gave White (Harikrishna) the chance to play with some hope and no risk for as long as he wanted. Eventually Dominguez made further errors, and Harikrishna earned a full point.
Naiditsch-So was an easy draw for Black in the Berlin ending, and Aronian didn't have much trouble drawing on the black side of a Trompowsky against Rapport. The other two draws were more interesting. Loek van Wely tried to blow Anish Giri off the board - also in a Trompowsky - and he was succeeding. 23.Bxe6 fxe6 24.f7+ Kh8 25.Ng5 would have proved that White's position was winning. Missing his chance, Giri was able to promote his b-pawn, forcing van Wely to go for perpetual check. Finally, Boris Gelfand bounced back from losses in the first two rounds to achieve a winning position with Black against Hikaru Nakamura. Unfortunately for the Israeli GM, he missed a nice win starting with 43...Bxf3+, and this game too was decided by perpetual check (or at least the threat thereof).
Six players are tied for first with 2/3: Aronian, So, Harikrishna, Caruana, Nakamura and Giri; Karjakin and Rapport are half a point behind. Tuesday is a rest day for the Masters Group but not the Challengers, and the reverse will be true on Wednesday.
Here are the round 4 pairings (on Wednesday) for the Masters Group: