Spassky-Fischer, World Chess Championship, Reykjavik 1972, game 5
The World Championship match from 1972 between the Soviet World Champion Boris Spassky and the challenger Bobby Fischer of the United States was labelled the Match of the Century. Before game five the score was 2,5-1,5 in Spassky's favour. In the presented fifth game of the match Spassky implemented a tricky novelty on move 11 in a positionally complex variation of Nimzo-Indian, but Fischer avoided the tactical trap and found the best response. Then the American perfectly used his opponent's inaccuracies to underline the strategic deficiencies of White's position and convincingly outplayed the reigning World Champion.
This loss with the white pieces in just 27 moves came as a real shock for Spassky, who then lost 3 out of his next 5 games, after which the match was practically decided in Fischer's favour.