The Zig-Zag Theory applies to NHL and NBA playoff series that follow the 2-2-1-1-1 format (which includes all NHL series, and all NBA series except for the Finals which are 2-3-2). Named the Zig-Zag Theory for its propensity of going up and down, the idea is that when betting on the playoffs, each game in the series is affected by the result of the game that preceded it.
NBA Zig-Zag Theory
Due to the power of home-court advantage in basketball, the value on a road team that loses game one isn’t as apparent until Game 3, as road teams that lose Game 1 win Game 2 only 31.5% of the time.
If the road team wins Game 1, the favorite is a very strong bet to bounce back, as historically they have won 76% of the time in that circumstance.
When the higher-seeded team leads the series 2-0 and must go on the road, this is a great spot to bet the lower-seeded team that is now playing at home. No team has ever come back from down 3-0 in a series in NBA history, so the desperation that sets in for the team down 0-2 is a huge boost. Despite losing the first two games, the lower-seeded team wins outright more than 62% of the time.
NHL Zig-Zag Theory
In the NHL, if the home team wins Game 1, the lower-seeded road game will win Game 2 nearly 35% of the time. Considering that Game 2 will feature a higher-seeded team at home coming off a win, the public is sure to love the favorite at home to win again, which often provides great value on an upset that happens more than 33% of the time. In the 2009-10 opening round, all eight winners of Game 1 lost Game 2, making a very strong case for the Zig-Zag theory.
There is no greater motivator in sports than the fear of elimination. As desperation sets in, playoff teams take their game to the next level, making the team coming off of a loss a great bet in both the NBA and NHL.