Seven months before the world title series Norway’s Magnus Carlsen and his US challenger, Fabiano Caruana, are in good form. The American is still benefiting from the momentum he achieved at the Berlin Candidates and in the Grenke Classic while Carlsen has been sparked by the emergence of a dangerous rival.

On Thursday night Caruana was sharing the lead in the US championship at St Louis on 5.5/8 with three rounds left while Carlsen, after a slow start in the Azeri elite event at Shamkir, had taken a clear 5.5/8 lead. Just one round remains there, but in Saturday’s ninth and final game Carlsen meets China’s Ding Liren, who is only half a point behind the world champion.

The final stages of both tournaments can be viewed free and live online this weekend with grandmaster and computer move-by-move commentaries.

Caruana has been impressive in his four game victories, notably crushing two French Defences 1 e4 e6, but his performance was blemished by a shock defeat from Zviad Izoria, a semi-retired Californian GM who won a long ending with a rook pawn which Caruana’s knight could not stop. Earlier Caruana declined a draw and admitted he lost his objectivity: “I just went crazy.”

Caruana’s elite GM colleague Hikaru Nakamura thought this game was ominous for the world title series in November: “It bodes poorly for the match because Magnus is very good at drawing out long games. That’s one of the big weaknesses Fabiano is going to have to work on.”

Sam Shankland, 26, was Caruana’s co-leader after eight rounds and created a stir when he declared that it was wrong to try to draw with the top-rated trio of Caruana, Nakamura and Wesley So because “they are also human beings. They can die.” These were brave words and, after halving with Caruana and So, Shankland launched a powerful attack against the out-of-form Nakamura, who needed all his experience to escape into a level ending. Shankland looked sure to take a shock half-point lead in Friday night’s ninth round (of 11) when he went a knight up with a winning game against Yaroslav Zherebukh while Caruana had only a level position against Nakamura.

Meanwhile nearly 90% of the games were drawn in the first six rounds at Shamkir, where Carlsen chose a waiting game. Norway’s world champion began with three blacks in the first four rounds, then made his move in the second half of the tournament where, in an ending of queen and pawn against Veselin Topalov’s rook and pawn, his winning idea to break the black fortress was to sacrifice queen for rook.

Before that, Carlsen unleashed a new anti-Sicilian idea to defeat Poland’s Radoslaw Wojtaszek.

His plan 5 Qd2!? (5 Bb5 is normal) followed by Bb2 and castling long set unfamiliar problems. Black’s 9…h6 counter was too sharp (better Be7) and Carlsen’s Nh3-g5 development was strong.

The legendary tactician Mikhail Tal had Nd5 sacrifices against the Sicilian as a trademark, but Carlsen flunked it at move 17 because he could not visualise all the complications. However, it was near winning after 17 Nd5! ed5 18 exd5 Nd8 19 Bd3! Rh5 20 Rxe7+! Qxe7 (Kxe7? 21 Qe2+ and 22 Qxh5) 21 Re1 Ne6 22 dxe6 with a decisive attack.

Black’s final error was 25...Rc5? when Qc5 may hold, and at the end Wojtaszek resigned because of 31…Kf6 32 g5+ Kxg5 33 Rxh1 or 31…Kd6 32 Rd8+ Kc6 33 Rc8+.

Magnus Carlsen v Radoslaw Wojtaszek

1 e4 c5 2 Nc3 d6 3 d4 cxd4 4 Qxd4 Nc6 5 Qd2 Nf6 6 b3 e6 7 Bb2 a6 8 O-O-O b5 9 f3 h5? 10 Nh3! Be7 11 Ng5 h4 12 f4 Bb7 13 Kb1 Rc8 14 Be2 Qc7 15 Rhe1 Nh7 16 Nxh7 Rxh7 17 g4? hxg3 18 hxg3 Bf6 19 Bd3 Rh8 20 g4?! Nd4 21 Re3 Kf8! 22 Ne2 Nxe2 23 Rxe2 Bc3 24 Bxc3 Qxc3 25 Qe3 Rc5? 26 e5! dxe5 27 fxe5 Rh1 28 Rxh1 Bxh1 29 Rh2 Rxe5 30 Rh8+ Ke7 31 Qa7+! 1-0

3564 1 Bh1! Kf4 2 Kg2! Ke4 3 Kg3 mate.