Still, when top players miscalculate badly, it can be a little comforting. (“Well, if they can do it, I don’t feel like such a patzer.”)

Last week, there were a number of such moments.

At the Tata Steel tournament in the Netherlands, Magnus Carlsen of Norway, the world’s top-ranked player, made a colossal mistake in Round 3 against Anish Giri, a 16-year-old Dutch grandmaster.

Carlsen was lackadaisical in playing the opening, but, as shown in the top diagram, he was not much worse off than his opponent. He should have tried 19 c4 when, after 19 … Nc4 20 Qb4 Nd6 21 Ba3, the game would have been a long way from over.

But Carlsen imploded by playing 19 Rd1, and the game ended 19 … e4 20 Ng5 e3 21 Qb2 Qg5 22 Be3 Qg4. Carlsen resigned because he could not make up for the knight he had lost. (Playing 20 Nd4 would have been better, though his position would still have been bad.)

And it would not have helped to play 22 Qb6 because after 22 … e2 23 Re1 Qc1 24 Rc1 e1/Q 25 Re1 Re1 26 Bf1 Bh3 27 Qb5 (the only way to avoid mate) Rf1, Black would have won easily.

At the same tournament, Daniele Vocaturo, an Italian grandmaster, got a gift-wrapped win in Round 4 from his opponent, Jan-Willem de Jong, a Dutch international master.

De Jong completely outplayed Vocaturo, arriving at the position seen in the bottom diagram after 25 moves. If he had continued 26 Rd1, then 26 … he could have won quickly. For example, after 26 … e3 27 f3 h4 28 gh4 Bf3 29 Rc8, White would have had too many threats for Black to parry. (Note that after 26 … e3, White should not play 27 Rd5 because 27 … ef2 quickly leads to checkmate after 28 Kg2 f1/Q 29 Kf1 Qe2 30 Kg1 Qe1 31 Kg2 Re2 32 Kh3 Qf1 33 Kh4 Rh2, mate.)

De Jong tripped up with 26 Ng7, and suddenly the tables were turned. The game ended 26 … Qe5 27 Nf5 Be6 28 Rfc1 Qf5 29 Qe3 Kg7 30 Ra7 Rc8. De Jong resigned because he had no compensation for his material deficit.

John Fedorowicz, an American grandmaster and coach, said there was no cure for such “chess blindness.”

“People have to remember how they lost,” he said, “and get aggravated and don’t do it again.”

Certainly Carlsen is unlikely to forget what happened to him against Giri. After he lost, he posted this message on Twitter: “Always nice to confirm that I’m still capable of blundering a piece in one move!”

This article has been revised to reflect the following correction:

Correction: January 23, 2011

In an earlier version of this article, he analysis of a game between Daniele Vocaturo, an Italian grandmaster, and Jan-Willem de Jong, a Dutch international master, in the Chess column on Sunday was incorrect. If de Jong had played 26 Rd1, then 26 … e3 27 f3 h4 28 gh4 Bf3 29 Rc8 would have given White too many threats for Black to parry.