Amazing moves in chess

I am currently reading a book about the 10th World Champion, Boris Spassky. I believe that his talent is generally underappreciated by the chess public. Of course, it does not help that he lost the title to Robert Fischer, who kind of overshadowed all of Spassky's previous achievements with his powerful rise to the throne.

However, at his peak Spassky played amazing chess. In fact, his style was (and still is) very difficult to describe. Most people just tend to say that he was a "universal" player, meaning that Spassky could do a bit of everything - attack, defence, strategy, tactics, a bit of psychology and sometimes all of that in a single game. 

In my opinion, Spassky played one of the most amazing moves in chess history. It took place almost 60 years ago, in the Soviet Union championship. Spassky shared the first place with Taimanov and Averbakh and thus this trio had to play an extra double round-robin to decide on the winner. Things did not work out well for Spassky in that tournament. He lost both games to Taimanov and even forfeited the last game vs Averbakh due to illness. However, the only game that he drew was indeed a special one.

The position on the diagram arose after White's 16th move. Black is standing much worse, because he does not have any counterplay, while White is about to crash through on the kingside. Realizing that normal play does not promise Black anything, Spassky calmly played 16...Nc6!!?

According to the reports, Averbakh was so shocked that he spent about an hour on his next move. Obviously, it wasn't spent on calculating variations, for White has no other options than to take the knight. After 17.dxc6 bxc6 Black was down a piece for just one pawn and some vague ideas of bringing his knight to d4 and rook to b8. However, this move rattled Averbakh so much that the course of the game took a dramatic turn. In the ensuing time trouble Spassky completely outplayed his opponent and even ended up with an extra exchange and pawn in the endame! Unfortunately, he could not convert this advantage and the game ended up in a draw.

Still, when I was looking at this game, I could not help but wonder - how could this idea even cross Spassky's mind? And what kind of guts should one have to actually play this on the board, in the top tournament against one of the strongest grandmasters of the time? Even Tal's famous sacrifices usually had some tactical justification behind them, but this?!..