If you love chess enough to play hundreds of tournaments you will, sooner or later, play like a numbskull. You lick your wounds, go to bed, and hope the engine belches into action the next day.

As a wise man once told me, the great comfort of a knockout tournament is that if you play badly, at least you get to go home. Except that doesn’t apply to Magnus Carlsen, or at least not yet. The world no. 1 is the top seed at the Fide World Cup, currently underway in Baku, Azerbaijan. But he suffered two serious glitches on consecutive days in his fourth round match against Germany’s Vincent Keymer, one of the world’s top juniors.

Vincent Keymer-Magnus Carlsen

Fide World Cup, Baku 2023

Keymer held a modest edge in the first game, until Carlsen blundered, playing 36…Nd5-c7 to reach the position in the diagram. Keymer pounced with 37 Nd6, attacking the pawn on b7. The kicker is that 37…Rb1 is met by 38 Rf5, and the f7-pawn can’t be defended, or 37…Ne6 38 Rf5 Nd8 39 Re5 Ne6 40 g6! is even worse. Carlsen tried 37…g6, but Keymer captured 38 Nxb7 and converted his extra pawn impeccably. Black resigns at move 58

Magnus Carlsen-Vincent Keymer

Fide World Cup, Baku 2023 (see diagram 2)

That left Carlsen needing a win the next day. In the diagram position, Carlsen has pushed 16 a2-a3, but soon realised that it was a lemon, since after Keymer’s response 16…Bxc3, all White’s recaptures are bad. Worst of all is 17 Nxc3 since 17…Qf4+ wins the Bh4, while recapturing with the pawn would gravely expose White’s king. Carlsen played 17 Qxc3 as nonchalantly as he could, but he knew that if Keymer spotted 17 …Nxe4! he was done for. After 18 Qxe5 Rxe5 19 fxe4 Rxe4 Black forks the Ne2 and Bh4, keeping a two pawn advantage. Or 18 fxe4 Qxe4 is similar, and in either case, Keymer would have been a huge favourite. Instead Keymer exchanged queens, and Carlsen won in 62 moves, to tie the match 1-1.

After the game, Carlsen lamented: ‘Honestly since day one I was wondering what am I doing here, why am I spending all this time playing classical chess which I just find stressful and boring.’ Carlsen has repeatedly expressed a preference for faster time limits such as rapid or blitz chess.

It was perversely predictable that Carlsen would beat Keymer in the tiebreak, and in the next round he dispatched the 54-year-old Ukrainian star Vasyl Ivanchuk with two wins in the classical games. As I write this, the quarter final is soon to begin, in which Carlsen will face another world-class teenager, Dommaraju Gukesh from India.