user-1: Taking the recent Anand-Carlsen match as an example, I know that grandmasters spend incredible amounts of time in opening preparation, and Anand's play to refute certain lines of the Berlin defense was impressive.
But once reaching game 10, 11, or 12 and desperately needing a win, why don't players make an effort to force the game off into some opening line that the opponent almost certainly hasn't prepared for? Not into some fringe or unorthodox opening, but into solid openings that are just much less familiar for the opponent.
Much the same way that an American football team must spend at least some small amount of time practicing "trick" plays, like on-side kicks or throw-back passes, or much like a football (soccer) team might practice very special free kick formation for late in a game when a goal is needed very quickly -- shouldn't it be normal to prepare for a championship match by spending at least a small amount of time studying some very different openings that the opponent has not faced recently or does not appear to be as strong in?
I'm not endorsing these as candidates for specifically Anand v. Carlsen, but I might have expected to see some different variations of Sicilian, or to see Dutch Defense, Benoni Defense, or to see Reti opening, and to play in lines that don't transpose easily to positions that are similar to the main lines played (Grünfeld, Berlin, etc.).
I'm not saying Anand's openings were the problem in the match -- he often played well with great opening prep and blundered later on. 
I am just asking why it is so uncommon to see players deviate to some "special preparation" in late stages of a match when they are trailing and need a win. 
Wouldn't that be one of the scenarios that they prepare for specifically prior to the match starting? "What if I find myself down 1 point late in the match and my opponent has shown clear strength in the most frequent openings from the match? How will I steer the game into unknown territory?"

user3270: I looked through the WC matches since 1995 (Kasparov-Anand) to try to validate the claim that surprise openings aren't used very often at the end of matches. I found that generally this holds true, with some notable exceptions. Particularly, in both of his WC matches where he trailed with two games to go, Vladimir Kramnik has pulled out sharp tactical openings that he rarely or never played previously.
In 2004 vs. Peter Leko (http://www.chessgames.com/perl/chesscollection?cid=1002400) he was down 6.5-5.5 in a 14-game match when he played a Benoni in game 13. While he did not win that game, he generated excellent chances and likely missed a win in the endgame.
In 2008 vs. Viswanathan Anand (http://www.chessgames.com/perl/chess.pl?tid=65865), he was down 6-4 in a 12-game match when he played a Najdorf Sicilian in game 11. He did not win that game either, but he certainly avoided his renowned Berlin or the Petroff.
In 2013, Anand was down 5-3 going into game 9 of a 12-game match against Magnus Carlsen (http://www.chessgames.com/perl/chess.pl?tid=81142) when he played the 4. f3 Nimzo. He got a strong attack but ultimately blundered and lost the game.
However, there is an additional reason that surprise openings do not appear often, which is that many matches are level towards the end and both players want to get to the tiebreaks without expending too much effort. I find this to be the case in Kramnik-Topalov 2006, Anand-Gelfand 2012, and Anand-Topalov 2010 (although Topalov badly blundered in the last game and lost).
That leaves the following matches where a surprise opening did not appear: Kasparov-Anand 1995 (the last few games were sharp Sicilians, which had been played several times in the match already), Kasparov-Kramnik 2000, and Carlsen-Anand 2014. In Carlsen-Anand 2014, Anand had been getting good play from his openings as White and I see no reason that he should have deviated.
That leaves the only really inexplicable case as Kasparov-Kramnik, where Kasparov seems to have just lost his will to dominate after the match started out badly. He had been the dominant player in the world for over a decade and maybe finally being brought low was too fatiguing for him.

user657: It happens, but there's a reason why it doesn't happen often, and, when it does, why it doesn't work.
First off, there's a psychological reason not to do it; it's uncomfortable. If the match is going badly for you, it's natural for you to fall back on familiar weapons: positions that you know how to play better than any others. When you do that, when you stand on familiar ("home," if you will) ground, you feel more secure and play better than if you're in less familiar territory. And when you play better, you're more likely to score better.
Also, there's the unknown. When you're down by a point late in the match, a single failure ends your chances. And, when you decide to divulge radically from your "normal" game approaches for this one game, you don't know with certainty how well your opponent can play those positions. So you divert time away from preparing to play comfortable positions even better than you currently play them (after all, no one plays their comfortable positions perfectly, there's always room for improvement) to learning how to play a completely different position passably well. And, when the day of the game dawns and you uncork it, you find out your opponent actually likes to play those positions, just never gets the chance to because opponents haven't so far let that happen. And down go your chances of leveling the match in a flaming crash.
Romantic notions like risking everything on one wild roll of the dice don't occur naturally to the vast majority of top chess players, because the tendency to do so keeps them from making it to the top, except in the rarest of circumstances.
A GM once told me chess was a little like tennis; "sometimes the only thing you can do is hit the ball back over the net and try to give your opponent another chance to make a mistake."
You're far more likely to see a player pull divergences like that that early in a match than late, such as Fischer pulling out 1.c4 to open Game 6 of the 1972 match (that match was for 24 games, so G6 there would have been like G3 of Carlsen-Anand). If it doesn't work, then the player still has the energy to save the draw if possible, and time to recover from the failure if not.

-1: <p>Taking the recent Anand-Carlsen match as an example, I know that grandmasters spend incredible amounts of time in opening preparation, and Anand's play to refute certain lines of the Berlin defense was impressive.</p>

<p>But once reaching game 10, 11, or 12 and desperately needing a win, why don't players make an effort to force the game off into some opening line that the opponent almost certainly hasn't prepared for? <em>Not</em> into some fringe or unorthodox opening, but into solid openings that are just much less familiar for the opponent.</p>

<p>Much the same way that an American football team must spend at least some small amount of time practicing "trick" plays, like on-side kicks or throw-back passes, or much like a football (soccer) team might practice very special free kick formation for late in a game when a goal is needed very quickly -- shouldn't it be normal to prepare for a championship match by spending at least a small amount of time studying some very different openings that the opponent has not faced recently or does not appear to be as strong in?</p>

<p>I'm not endorsing these as candidates for specifically Anand v. Carlsen, but I might have expected to see some different variations of Sicilian, or to see Dutch Defense, Benoni Defense, or to see Reti opening, and to play in lines that don't transpose easily to positions that are similar to the main lines played (Grünfeld, Berlin, etc.).</p>

<p>I'm not saying Anand's openings were the problem in the match -- he often played well with great opening prep and blundered later on. </p>

<p>I am just asking why it is so uncommon to see players deviate to some "special preparation" in late stages of a match when they are trailing and need a win. </p>

<p>Wouldn't that be one of the scenarios that they prepare for specifically prior to the match starting? "What if I find myself down 1 point late in the match and my opponent has shown clear strength in the most frequent openings from the match? How will I steer the game into unknown territory?"</p>
 3270: <p>I looked through the WC matches since 1995 (Kasparov-Anand) to try to validate the claim that surprise openings aren't used very often at the end of matches. I found that generally this holds true, with some notable exceptions. Particularly, in both of his WC matches where he trailed with two games to go, Vladimir Kramnik has pulled out sharp tactical openings that he rarely or never played previously.</p>

<p>In 2004 vs. Peter Leko (<a href="http://www.chessgames.com/perl/chesscollection?cid=1002400" rel="nofollow">http://www.chessgames.com/perl/chesscollection?cid=1002400</a>) he was down 6.5-5.5 in a 14-game match when he played a Benoni in game 13. While he did not win that game, he generated excellent chances and likely missed a win in the endgame.</p>

<p>In 2008 vs. Viswanathan Anand (<a href="http://www.chessgames.com/perl/chess.pl?tid=65865" rel="nofollow">http://www.chessgames.com/perl/chess.pl?tid=65865</a>), he was down 6-4 in a 12-game match when he played a Najdorf Sicilian in game 11. He did not win that game either, but he certainly avoided his renowned Berlin or the Petroff.</p>

<p>In 2013, Anand was down 5-3 going into game 9 of a 12-game match against Magnus Carlsen (<a href="http://www.chessgames.com/perl/chess.pl?tid=81142" rel="nofollow">http://www.chessgames.com/perl/chess.pl?tid=81142</a>) when he played the 4. f3 Nimzo. He got a strong attack but ultimately blundered and lost the game.</p>

<p>However, there is an additional reason that surprise openings do not appear often, which is that many matches are level towards the end and both players want to get to the tiebreaks without expending too much effort. I find this to be the case in Kramnik-Topalov 2006, Anand-Gelfand 2012, and Anand-Topalov 2010 (although Topalov badly blundered in the last game and lost).</p>

<p>That leaves the following matches where a surprise opening did not appear: Kasparov-Anand 1995 (the last few games were sharp Sicilians, which had been played several times in the match already), Kasparov-Kramnik 2000, and Carlsen-Anand 2014. In Carlsen-Anand 2014, Anand had been getting good play from his openings as White and I see no reason that he should have deviated.</p>

<p>That leaves the only really inexplicable case as Kasparov-Kramnik, where Kasparov seems to have just lost his will to dominate after the match started out badly. He had been the dominant player in the world for over a decade and maybe finally being brought low was too fatiguing for him.</p>
 657: <p>It happens, but there's a reason why it doesn't happen often, and, when it does, why it doesn't work.</p>

<p>First off, there's a psychological reason not to do it; it's uncomfortable. If the match is going badly for you, it's natural for you to fall back on familiar weapons: positions that you know how to play better than any others. When you do that, when you stand on familiar ("home," if you will) ground, you feel more secure and play better than if you're in less familiar territory. And when you play better, you're more likely to score better.</p>

<p>Also, there's the unknown. When you're down by a point late in the match, a single failure ends your chances. And, when you decide to divulge radically from your "normal" game approaches for this one game, you don't know with certainty how well your opponent can play those positions. So you divert time away from preparing to play comfortable positions even better than you currently play them (after all, no one plays their comfortable positions perfectly, there's always room for improvement) to learning how to play a completely different position passably well. And, when the day of the game dawns and you uncork it, you find out your opponent actually likes to play those positions, just never gets the chance to because opponents haven't so far let that happen. And down go your chances of leveling the match in a flaming crash.</p>

<p>Romantic notions like risking everything on one wild roll of the dice don't occur naturally to the vast majority of top chess players, because the tendency to do so keeps them from making it to the top, except in the rarest of circumstances.</p>

<p>A GM once told me chess was a little like tennis; "sometimes the only thing you can do is hit the ball back over the net and try to give your opponent another chance to make a mistake."</p>

<p>You're far more likely to see a player pull divergences like that that early in a match than late, such as Fischer pulling out 1.c4 to open Game 6 of the 1972 match (that match was for 24 games, so G6 there would have been like G3 of Carlsen-Anand). If it doesn't work, then the player still has the energy to save the draw if possible, and time to recover from the failure if not.</p>
