NFL first-half betting, Part Two

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.

Weaker sportsbooks may move their first-half lines due to small action. If a square bets the wrong side for an amount that the sportsbook considers large (but not necessarily an amount that you would consider large), the sportsbook may move the line to a point where there is positive value for you to jump in and play.

When the game line is moved, sportsbooks may be slow to move the first-half line. Many sportsbooks are slow to move the money line when they move the point spread; the first-half lines are even farther from their minds. This strategy can be particularly valuable when a line has been taken off the board due to a potential injury. Once the injury news is known, if the new line is considerably different from the old line, then the first-half line should be adjusted also. But some sportsbooks reopen the game line and forget to adjust the first-half line until someone makes a bet. They may catch the error and refuse the bet, or they may take the bet and then change the line. A good relationship with the sportsbook manager will help in situations like this.

When you have an opinion on a game and you are looking to make a wager, compare the first-half line to the game line; there may be more value in the first-half line. For example, if the line is the Vikings -5 -110 in the game, but the first-half line is the Vikings -2.5 -110, there is better value in betting the first half. It may turn out that the Vikings cover the 5 points in the game but don’t cover the 2.5 points in the first half, thus turning a winner into a loser; but it is more likely for the Vikings to cover the 2.5 points in the first half and not cover the 5 points in the game, turning a loser into a winner.

Proceed with caution if you think there is something specific about the game that is different from an average game with respect to the first half versus the second half. For example, say a team has lost two double-digit leads in the second half in the last few games. These collapses are going to be on their minds. If they are up big in the first half again, they may be less likely to let up in the second half. If the point spread in the game reflects this attitude, then the relationship of the game line to the first-half line may not be like that of the average game.

A team has a playoff spot and position locked up going into the last week of the regular season may not play to win as it normally would. Sometimes the first-string players will play only a portion of the game while the back-up players play most of it. These teams do not have winning as a primary goal, so the relationship between the first half and the game will not be like a typical NFL regular-season game.

Conclusion

There are still some opportunities in first-half lines, but they have decreased over the years as sportsbooks and bettors get more sophisticated. But this information can still be useful in comparing value for half-point differences in first-half lines as well as comparing relative value between game lines and first-half 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.