It was an exciting day of tiebreaks, though it was disappointing that only one match made it past the two 25-minute games, and it was settled in the 10' + 10" round. We need to see at least one Armageddon game before the tournament ends!
Anyway, to the round. Peter Svidler had the easiest time of it, beating Bu Xiangzhi 2-0. In the first game, Svidler won with Black after Bu got tangled up in the center. White tried to bail out with an exchange sacrifice, and it almost worked. Bu was about to esacape until he played 40.Ra5??, walking into a lethal self-pin. Walking into mate in one on the next move didn't help, but the damage had already been done - even 41...Rb4 would have done the job. In the second game, Bu tried the Dutch, hoping for a complicated position, but when he met the Improved Lisitsyn Gambit by turning the game into a Philidor Counter-Gambit he got in trouble - fast. He was already clearly worse by move 7 (maybe by move 5, but let's be generous), and after a huge error on move 9 he was completely lost. Svidler may not have played in the most incisive way, but he didn't have to, and he coasted to victory.
Wesley So was also a smooth winner, outplaying Baadur Jobava in their first game with the white pieces, demonstrating the power of the bishop pair (and later of bishop vs. knight) to grind out a victory. Game two was an "I'll make you an offer you can't refuse" draw: So was better from early on, and could have played for a win had he needed to. Instead, he allowed Jobava to draw by repetition in a position where he was still better, but the problem for Jobava was that varying from the repetition would lose on the spot.
In one of the matches featuring underdogs, Evgeniy Najer held an edge in his white game with Richard Rapport until his ill-advised 23.Bxh6, which should have been met by 23...Rxf3. For a while after that Najer had good chances to win, but Rapport gradually clawed his way back to equality and a draw. The second game was completely crazy, and Rapport handled the complications much better than Najer to win deservedly. There was one big hiccup near the end, however. 45.Rb7+ followed by 46.Re2 won comfortably, but after his 45.Rb6? Najer had 45...Re1+ first, and only after 46.Kg2 was 46...Nb4 correct. In this case he would have equalized. Now White can't play Re2, and if he takes on a5 Black has an immediate perpetual with his rook going to e2, e1 and/or e3, as needed.
In the other battle of the underdogs, Vladimir Fedoseev defeated Maxim Rodshtein 2-0, though unlike Svidler's 2-0 victory it wasn't easy. First of all, it's a mystery why Rodshtein didn't play 37...Qxc3 in the first game, leading to a dead draw after 38.Rxc3 Bxf2 39.Nxe6 Rxc3 40.Bxc3 fxe6. Even after 37...Bxc7 39.Bxc7, trading queens would have given him excellent drawing chances in the opposite-colored bishop ending. The draw wouldn't be guaranteed on account of the rooks, but keeping queens on as well made it harder, not easier, for him to defend. Eventually the queens came off, but under more favorable circumstances for Fedoseev. It still wasn't easy for White to win until Rodshtein's 69...Kf7, allowing White to play 70.Rf8+ and 71.Rf6. After that, the conversion was routine. Rodshtein did a great job of creating a complicated mess in game two, and he had good chances to win as soon as the early middlegame. The game went back and forth, and Rodshtein missed a very good chance on move 33, when taking on b5 followed by d6 would give him a winning advantage. From there on, he played too passively, and Fedoseev took over the initiative. White had to play 41.Bg2 to stay alive, and after missing that chance he resigned three moves later.
Finally, in a match that would have been better as a semi-final or even a final, Maxime Vachier-Lagrave and Alexander Grischuk had a heavyweight battle in keeping with their ratings. They drew the 25-minute games, and saved the best for last. In the first 10-minute game, Grischuk's attempt to solve his strategic problems with tactics failed. In particular, 28...Rg6, going for counterplay, was strongly met by a great pawn sacrifice from MVL. From 30 to the end of the game, Vachier-Lagrave blew his opponent off the board with one threat after another in a great display of the power of the initiative. The second game was a battle between the initiative - again, on MVL's side - and static goods. Grischuk's 10.Bxc6 wrecked Black's queenside structure, but at the cost of the bishop pair, weak light squares, and a few moves later, a badly sidelined queen. Vachier-Lagrave found a great exchange sac, but misplayed it a few moves later and wound up in an inferior ending. After two further inaccuracies, he wound up in a lost ending with bishop and pawn against Grischuk's rook and pawn. Grischuk made a very serious practical error when he didn't play 44.h3, after which proving a win with hardly any time on his clock was as good as impossible, and MVL advanced to the fifth round.
The games are here, but I've only annotated the second Svidler-Bu Xiangzhi game, along with the two MVL-Grischuk 10-minute games.
Tomorrow the quarter-finals begin, with these pairings (in bracket order): Svidler - Vachier-Lagrave, Ivanchuk - Aronian, So - Fedoseev, Rapport - Ding Liren.
Will Svidler continue his question to reach his fourth consecutive Candidates event? (Admittedly, once he was the organizer's wildcard pick, but the other two times he qualifed through the World Cup.) Or will Vachier-Lagrave stay alive as he hopes to reach the Candidates for the first time in his career? Can Ivanchuk survive the top remaining seed, Aronian, and show that his glory days are still going? And will the young upstarts Fedoseev and Rapport (22 and 21 years old, respectively) be put in their place by their elderly opponents (So and Ding Liren; 23 and 24 years old, respectively)?