The zig-zag theory for the NBA Playoffs can be expressed in a single sentence: Bet on the team that lost their last game. Obviously, you can’t bet it in Game 1 of any series, but starting with Game 2, the theory holds a significant influence on the betting marketplace.
The thought process behind the theory is simple as well. A team that just lost is likely to dig deep and produce a strong effort, before they fall into a deeper hole. Meanwhile, the team that just won is likely to make fewer adjustments and be a tad bit complacent heading into the next game.
The betting marketplace respects this theory tremendously. That's why you'll normally see a pointspread adjustment from Game 1 to Game 2, like Denver moving from +6 in Game 1 to +4/4.5 in Game 2 at Oklahoma City, or Portland moving from +5/5.5 in the opener to +3.5 in Game 2 at Dallas.
In addition, you'll often see the weaker of the two teams favored if they return home facing an 0-2 series deficit after losing the first two games on the road. Look no further than the Knicks opening as home favorites over Boston in Game 3 as a prime example.
Wiseguy bettors know that the zig-zag theory is going to influence pointspreads throughout the postseason. They'll understand why and how the books are making adjustments to the spread from game to game as a series progresses. And yet the theory itself hasn’t earned a profit for more than a decade; a classic case of the betting markets adjusting to current realities without bettors themselves realizing what has happened.
The NBA zig-zag theory was a big moneymaker in the 1980’s, when it wasn’t widely known or publicized. By the 1990’s, the increasing sophistication and the constant nature of adjustments within the betting markets led to a period of decreasing returns.
A recent database study showed that in playoff games from 1991-2000, the zig-zag went 311-249-19, producing a 55.5% ATS result with a sample size of nearly 600 games. And we shouldn’t forget that many bettors who didn’t have access to multiple pointspreads from varying sportsbooks did much worse than that – losing on many of the plays graded as a push in the database, and pushing on a handful of plays that were graded as wins.
Over the last decade, from 2001-2010, blindly betting the zig-zag theory went 331-317-9, 51% ATS winners. We all know that at the standard 11-to-10 sportsbook formula (ignoring offshore ‘reduced juice’ shops and betting exchanges), you have to hit 52.4% of your wagers to break even. If you’ve been blindly betting the zig-zag theory for the last decade, you’ve lost money.
And yet the theory still seems to hold a magical sway over many bettors. You can’t read an NBA Playoff betting article without some reference to the zig-zag, much like you can’t find a Monday Night Football discussion without some mention of the home underdog angle – which was debunked
in a Sportsmemo blog posted by Tim Trushel last September. Bettors need to know that these theories are completely outdated.
Blindly betting zig-zag won’t make you any money at all. In fact, if you’ve been zig-zag betting the Game 2’s so far this year, you’ve gone 2-6 ATS. The Knicks and Pacers were the only two winners; while these Game 1 losers – the 76ers, Magic, Blazers, Spurs, Nuggets and Lakers – all lost ATS. I wouldn’t count on significantly better returns in the Game 3’s over the next few days.