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And now, instead of 8 Qc2?, why didn’t White play the simple 8 cxd5 – ? This clearly wins a pawn without any complications; Black has absolutely no compensation at all.

I’m always amazed whenever I find a strong player committing an “inexplicable” oversight like this one that Najdorf made in this game. To clarify: in my opinion there are 4 factors which – when they are ALL present – combine to make an oversight “inexplicable”:

1] the STATURE of the PLAYER – generally not less than “master” level, when the game took place.

This means that, when the game was played, the player committing the oversight was AT LEAST what I’ll generically call “master” strength – whether that means a U.S. Chess Federation “NM” (‘National Master’) or a World Chess Federation “FM” (‘FIDE Master’, which is roughly a class stronger – about equal to USCF’s “SM”, for ‘Senior Master’). In some cases the player was actually ‘world-class’, i.e. one of the top players in the world at that time (as is true of Najdorf here).

2] the TIMING of the oversight – early in the game rather than late.

The lapse occurred somewhere in the early phase of the game before any real complications had developed; sometimes the players were still completing their development (as in this game). Thus, three things were clearly true at the time the oversight occurred:

A] the position had NOT yet become what experienced players would call a “tactical” (tactically complex) position.

B] the player making the oversight should NOT yet have been experiencing “mental fatigue”.

C] the player making the oversight should NOT yet have been in “time trouble” (see point #4 which relates to this).

3] the NATURE of the oversight – failing to spot something “obvious” which the most elementary calculation would’ve seen, very easily.

I’m NOT talking about every single occasion where, for instance, a player failed to see even a half-move ahead (i.e. his opponent’s reply) – because at times that reply can be subtle or unexpected (perhaps seeming ‘anti-positional’ or ‘unnatural’ or violating some principle – like in L Christiansen vs Karpov, 1993 where Black’s 11th move had overlooked White’s unnatural-looking 12 Qd1, which was obviously crushing once you saw it). But rather I’m talking about occasions where a “strong” player (I defined this factor in point #1) somehow overlooked a short & simple move-sequence that was COMPLETELY NATURAL – such as the missed opportunity in this game, “I play 8 PxP on d5, then he recaptures 8..PxP on d5, then I play 9 NxP on d5 and I’ve won a pawn” – and thus missing a chance to win material EFFORTLESSLY. I’m talking about “elementary” visualization that you’d expect all players to routinely demonstrate, except for *extremely* low-rated players and brand new novices.

4] the TIME LIMIT used in the game – standard “classical”, not accelerated.

It’s an acknowledged fact (as documented by computer analysis) that in games played using faster TLs, as expected the percentage of tactical errors increases. Even players of “master” strength and above (see point #1) can miss really simple tactics in “rapid” games, and even more so when playing “blitz”. Any game where I’ve labeled an oversight as “inexplicable” will be a game which had used the standard “slow” TL (which Chessgames calls “classical”).