Must-Win Games

King Yao is the author of Weighing the Odds in Hold‘em Poker, and Weighing the Odds in Sports Betting. He uses his experience from making millions in financial derivative markets and translates it into gambling. Since he left his trading position in 2000, he has been playing poker and betting on sports. He travels to Las Vegas frequently, especially during football season.

Must-win games are games where a loss results in the end of the series or falling behind so much that it is nearly impossible to come back. In the NBA, the lines in these games often lean towards the team that needs the win.

Game 3, home team down 0-2

In 54 games, the home team has a straight-up record of 34-20 and an Against The Spread (“ATS”) record of 34-19-1. The average line in these game 3s was the home team laying 0.65 points.

In game 4 of those same series after the home team won game 3, the average line shifted to the home team getting 0.21 points. That game-to-game line shift of 0.86 points indicates that the betting market is aware of the must-win situation in game 3 for home teams down 0-2.

Game 4, home team down 0-3

This is a must-win situation. If the home team loses, it is out of the playoffs. But instead of playing harder, as generally happens in must-win situations, the 0-3 home team seems to play with less intensity. Perhaps the players think that being down 0-3 is too large of a hole to dig out of. No NBA playoff team has ever come back from a 0-3 deficit to win the series.

The database shows 15 games where the home team was down 0-3. In those 15 games, the average line was home team +3.47, up from an average line of +0.67 in game 3. (The average over all game 3s with a 0-2 home team was home team -0.65; +0.67 applies to only the subset of those games in which the home team lost game 3.) That is a whopping game-to-game line shift of 2.8 points! The market expects a team down 0-3 to give less than full effort. Even with the extra points, the home team has had a tough time covering; its game-4 ATS record was 5-9-1. That sample size is too small for us to draw firm conclusions.

Game 6, home team down 2-3

When the home team is down 2 games to 3 going into game 6, the average line has the home team laying 1.8 points. In game 4 when the same team is at home, the average spread is home team by 1.2 points. Thus the home team is favored by 0.6 extra points in game 6 when down 2-3 in the series. The must-win situation is probably the reason for this difference.

Game 7

Game 7 is the deciding game of the series; it is a must-win game for both teams. Both games 5 and 7 are played in the same venue, so it is interesting to compare the difference in the point spreads in those two games. Only 19 game 7s were played in the NBA in the years studied, but even with this small sample size, the line movement is interesting.

Averaging the lines in all game 7s, the home team was a 4.5 point favorite. In the average game 5 in every series that had a game 7, the home team was a 5.3 point favorite. The home team was a smaller favorite in game 7 by 0.8 points. In those 19 instances of game 7, the home team had an ATS record of 11-7-1.

Perhaps the market erred in making the home team less of a favorite in game 7, but the sample size is too small to say for sure. The average line shift from game 5 to game 7 may be useful in calculating exact series lines.

This is part of an occasional series of articles.

Excerpted with permission from the e-book version of Weighing the Odds in Sports Betting by King Yao, edited for this format.