Anatoly Karpov won Game 23 of the world chess championship yesterday in Lyon, France, exemplifying -- whether he knows it or not -- Yogi Berra's dictum that it isn't over until it's over. The game, which lasted only 29 moves, was the quickest victory in the match.

Karpov's victory will push the match to its limit of 24 games, although the question of who will be the champion for the next three years was settled on Wednesday when incumbent Gary Kasparov played to a draw and raised his score to 12 points.

The most Karpov can hope to do, if he wins Game 24, is equalize the match score, which now stands at 12-11 in Kasparov's favor. That outcome would leave the title in Kasparov's hands but would reduce his winnings and raise Karpov's by $200,000.

If Kasparov wins a match victory, with 12 1/2 or 13 points, his prize is $1.7 million and Karpov's is $1.3 million. If the final score is 12-12, the $3 million fund is divided evenly.

In addition, Kasparov receives the Korloff trophy, a gold-and-bronze sculpture studded with diamonds and valued at $1 million, only if he scores a clear match victory. If Karpov wins Game 24, a playoff may be held later to dispose of this trophy.

In this game, Kasparov played quite well for the first 14 or 15 moves, but after that his form completely collapsed. In a King's Indian Defense, Saemisch Variation, his 8. . . . Qh4ch made fans wonder whether he might revive a queen sacrifice on move 9, first played 34 years ago by David Bronstein and played against Kasparov last year by American grandmaster Yasser Seirawan. This well-known combination starts with 9. . . . Nxg3; 10. Qf2, Nxf1; 11. Qxh4, Nxe3, and black has compensation for the two pieces. But the world champion, needing only a draw, backed off from this adventure and chose the quiet 9. . . . Qe7.

Karpov sharpened the play with his 11. exf5, and with 12. Nh3 he prepared a five-move strategic plan to make a pawn break with g4. This kind of strategic plan was used in the 1950s. The idea is, at the end, to get control of the square e4. When Karpov played 17. g4, white already seemed slightly ahead and Kasparov might have thought of a more radical approach to the game. He reacted thematically with 17. . . . e4, but 19. . . . Na4 did not look like Kasparov playing. On a better days he might have considered a pawn sacrifice: 19. . . . Nd3ch, opening more lines in the center.

Instead, he managed to double Karpov's pawns on the c-file, but with many pieces on the board and white enjoying a space advantage, Kasparov was unable to explore this weakness. His 22. . . . c5 was designed to take the square d4 from white's pieces. From move 23 on, even making allowances for a very difficult position, nobody would have thought a world champion was playing black.

With 24. h4, Karpov was ready to march his h-pawn to h6, a threat of penetration as slow and inexorable as an attack with tanks. Kasparov decided to open up the game, but the shocking way he did it amounted to a blunder. Some day, he may explain what he meant in sacrificing a piece with 25. . . . Bxd5, but nobody else can. His 26. . . . Rac8 was equal to resignation, but even 26. . . . Qa3ch, 27. Kb1, Qxc3 would have been decisively met by 28. Bd4.

Karpov could have played his crushing blow Bd4 at move 27, but he has been a master at dominating his opponents for the last 20 years, so he found an even better move, 27. Qd6. The key move 29. Bd4, slightly delayed, was icing on the cake.

The final game is scheduled for Monday but may be postponed because of the New Year holiday. The prolongation of the match (and postponement of the prize award) into 1991 would have still uncalculated effects on the two players' tax situations. Kavalek is an international grandmaster; McLellan is a Washington Post staff writer.