Exact Series Lines in the NBA, NHL, and MLB

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.

Exact Series Lines

For playoff series in the NBA, NHL, and MLB, sportsbooks often offer money lines on which team wins the series as well as exact series lines, which are lines on whether a certain team will win the series in a specific number of games. For example: “Yankees to win the ALCS in six games +150.” If the Yankees win the ALCS, but not in six games, then this bet is a loser.

A sportsbook may update the series money line and the exact series lines after every game. The series money line and the exact series lines are connected. The money lines for the individual games are connected to both the series money line and the exact series lines. Sometimes a sportsbook puts up lines that conflict with each other. You can take advantage of these situations by understanding how these three bets are connected. The current game line is likely the most efficient because the most money is being bet on it. Try to predict lines for the games yet to be played. Then calculate the series money line as well as the exact series lines for all possibilities. The difficult part is predicting the lines in the games yet to be played. Here is an example.

The Mavericks were playing the Suns in the NBA Western Conference Finals. The series is tied 2-2 with games 5 and 7 (if necessary) in Dallas and game 6 in Phoenix. The mid-market money line on game 5 is the Mavericks -300, indicating the market thinks the Mavericks have a 75% chance of winning game 5. In order to estimate the series line and the exact series lines, you must project the expected money lines for games 6 and 7. Here are my projections and the reasoning behind them.

Game 6

In games 3 and 4, with the Suns at home, the line was the Suns pick ’em and +1, respectively. Game 6 is a different situation because it will be an elimination game for one team or the other.

Since the Mavericks are heavy favorites to win game 5, the Suns are more likely to be the team facing elimination in game 6. Thus the line for game 6 is expected to be tilted more towards the Suns than games 3 and 4, and they are likely to be favored.

If the Mavericks win game 5, it would not be surprising to see the Suns as a 1 point favorite in game 6. The Suns will get more respect from the line makers and bettors due to the emotional factor of having their backs to the wall in an elimination game. Also, the zigzag theory is well known in the NBA playoffs; most bettors and bookmakers expect the team behind in the series to play with more energy and focus.

On the other hand, if the Suns win game 5, then it would not be surprising to see the Mavericks as a 1 point favorite in game 6. The Mavericks would have the emotional energy to play harder.

A one-point favorite equates to -107 in the money line or 51.7%. If the Mavericks win game 5, they will be pegged with a 48.3% chance to win game 6. If the Mavericks lose game 5, then they will be pegged with a 51.7% chance to win game 6.

Game 7

In order for there to be game 7, the Suns and Mavericks must win one game apiece in games 5 and 6. For game 7, the zigzag theory will no longer affect the line because it is an elimination game for both teams. Thus game 7 should differ from game 5 in that both teams should be equally motivated. In game 5, the Mavericks are a 7 point favorite, or -300 in the money line. Let’s make them favored by less in game 7; make them a 6.5 point favorite and -270 in the money line (73%).

Calculations

Now you have all the numbers needed to make the calculations. These numbers assume there are no injuries to the key players or other factors that could cause a big change in market perception.

Game 5: Mavericks 75%, Suns 25%

Game 6 if the Suns win game 5: Mavericks 51.7%, Suns 48.3%

Game 6 if the Mavericks win game 5: Mavericks 48.3%, Suns

51.7%

Game 7: Mavericks 73%, Suns 27%

Here are the ways that the Mavericks can win the series and their corresponding percentages:

Scenario 1

Game 5: Win 75%

Game 6: Win 48.3%

75% x 48.3% = 36.2%

Scenario 2

Game 5: Win 75%

Game 6: Lose 51.7%

Game 7: Win 73%

75% x 51.7% x 73% = 28.3%

Scenario 3

Game 5: Lose 25%

Game 6: Win 51.7%

Game 7: Win 73%

25% x 51.7% x 73% = 9.4%

Add up the percentages in all three scenarios, and the probability that the Mavericks win the series is 73.9%.

36.2% + 28.3% + 9.4%

= 73.9% or -283

The series money line at a major sportsbook before Game 5 was Mavericks -310, Suns +270. The numbers calculated above are right in line with the market. In general, series lines are fairly efficient; it is tough to find an edge big enough to bet on.

With only three games left, it is easier to evaluate the exact series lines than before the series started. With the numbers above, the calculations for the exact series lines are as follows:

Mavericks win in 6 games:

= 75% x 48.3%

= 36.2% or +176

Mavericks win in 7 games:

= (75% x 51.7% x 73%) + (25% x 51.7% x 73%)

= 28.3% + 9.4%

= 37.7% or +165

Suns win in 6 games:

= 25% x 48.3%

= 12.1% or +726

Suns win in 7 games:

= (25% x 51.7% x 27%) + (75% x 51.7% x 27%)

= 3.5% + 10.5%

= 14.0% or +614

Check to see if the lines are consistent with each other in case you made an arithmetic error. Add the probability of the Mavericks winning in 6 and 7 games, and see if it is the same answer as the Mavericks to win the series.

In this case it is:

Mavericks in 6 + Mavericks in 7 = Mavericks to win the series

36.2% + 37.7% = 73.9%

Suns in 6 + Suns in 7 = Suns to win the series

12.1% + 14.0% = 26.1%

73.9% + 26.1% = 100%

Generally only sharper sportsbooks offer updated lines on exact series lines. However, you can sometimes find value. After game 4, I was able to find one sportsbook offering the Mavericks in 6 at +200. I bet it since I thought I had 24 cents of edge. I won the bet when the Mavericks won the series in game 6. After the Mavericks won game 5, the game-6 line opened with the Suns -1 , as I expected. The line drifted to Suns -1.5 by game time, so my edge might have been smaller than 24 cents.

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.