Sports Betting: NFL Props Explained Part 2 Print
Written by TheSpread   
Friday, 08 December 2006 08:00
Sports Betting Top Stories

Part 2 in Our Series Covering The Mystery of NFL Prop Betting

Last week’s Pinnacle Pulse, introduced some ideas about how to gain an advantage from the increasingly popular “Which team will score first” prop. This week, we’re sticking with the theme and providing further hints on how to successfully price other common props available at PinnacleSports.com.

One of my personal favorites is the proposition: “Will the first score be a Touchdown or FG/Safety”. As a starting point for weighing this bet, you should look at how many TDs, FGs and Safeties have been scored by all teams in the season to date. Before this week’s Monday night game, the frequencies of each scoring play were as follows:

Fig 1

Up to Week 13

 

Touchdowns

 

Field Goals

 

Safetys

 

Frequency

 

848

 

546

 

13

 

%

 

60.3

 

38.8

 

0.9

 

This provides a good “baseline”, but there are two adjustments to be made to refine the data for an accurate assessment of the proposition.

First, the last two possessions of the half are more likely to result in a field goal than at any other time in a football game (except overtime). This bias isn’t simply due to  time running out - in many cases, teams will use conservative play-calling to ensure a field goal attempt. As a result, 50% of the time the last score of a half is a field-goal.

Since close to 40% of all scores are FGs or Safeties (fig 1), and it’s been established that the final score of each half is a FG 50% of the time, we’re in a position to work out how likely the first score is to be a FG by using simple algebra and the average number of scores by game.

We can work out an “average” score value using the %’s from fig 1.

(60% * 7 points/TD + 40% * 3 points/FG = 5.4 points/possession).

Historical data indicates that a ‘typical’ game averages a total of 41 points, so you would expect 7.6 scores – average total points scored/average score per scoring possession (41 / 5.4). You’d also anticipate 3.04 FGs – average number of scores * FG frequency % from fig 1 (7.6 * 0.4). From this we can work out the odds (x) of a FG being scored in any scoring possession, excluding the last score of the half.

3.04 FGs (per 7.6 scores) = 6.6 scores not at end of half * (x) + (1 end of half score) (0.5)

X = (3.04 – 0.5) / 6.6 = 0.385 (38.5%), or about +160 for a FG.

Now, you have to adjust this number for the actual match-up. For example, take a look at next week’s Monday Night match-up between the Bears and Rams. You need to look at TDs and FGs for each team’s offense and defense for this season.

Fig 2

 

Scored

Conceded

 

 

TD’s

 

FG’s

 

TD’s

 

FG’s

 

Bears

 

34

 

26

 

15

 

15

 

Rams

 

23

 

27

 

33

 

18

 

Total

 

57

 

53

 

48

 

33

 

Since we do not care who scores what (only which is scored first), we simply add the total TDs and FGs from Fig 2 - 105 TD’s (57+48) versus 86 FG’s (53+33). 45% of the scores involving these two teams were Field Goals, compared to 40% for the league average. If 45% were the result of thousands of games, you would expect that to go forward. However, each team has only played 12 games, so expect this percentage to “revert to the mean”. One way to do this is to average the two (40 + 45) / 2) which suggests 42.5% of all scores in this match-up will result in a FG. For the first possession, start with the baseline first possession FG score frequency of 38.5%, and multiply by the mean FG expectancy for these teams calculated above (42.5/40 *0.385) = 40.9%. This is equivalent to +144, which is my price for a FG being the first score of the game.

Once you have your no-vig price (+144/-144), try to find a line that is 10 cents off. If you found “first score TD” at -134 or better, or “first score FG/Safety” at +154 or better, it might warrant a play in this match-up.

There are also several ways to improve this result. You can track safeties, or do statistical studies on scoring for many years to plug more accurate averages into the calculations. There are other statistical methods you can use to get even better results. However, when you’re tackling props, you want to evaluate them without spending an inordinate amount of time as you’ll make more money by pricing 10 different props well, than by analyzing 1 prop perfectly.

 

What are players betting at Pinnacle Sports this week?

Cleveland +9 -129 v. Pittsburgh

We initially offered Cleveland at +9 (-112). Using this unusual number (instead of +7 ½ at a normal moneyline) helps protect us on teasers, as teasing “large home favorites” is one of the strongest teaser plays you can make.

The opening number of Cleveland at +9 (-112) is equivalent to +8 (-105) using Pinnacle’s point-selling option. While the betting public strongly favors Cleveland by a 15:1 margin, some of the early sharps are playing Pittsburgh.

Indianapolis -1 -112 v. Jacksonville

This game has remained at the current price (-1 -112) since opening. Once again, teaser protection is a concern. While small underdogs are not as dangerous as large home favorites, we would still prefer to minimize damage from these types of plays. Skewing the line this way is an easy way to achieve this. While bettors favor the Colts by a 5:2 margin, the line has not moved. The early sharps have been on both sides of the game, so it’s anyone’s guess where this one is headed.

USC +1 -103 v. Michigan

After UCLA stunned USC and Florida beat Arkansas, both of these former championship contenders had to settle for the Rose Bowl. Michigan’s omission from the title game has caused controversy over the BCS selection process and it appears that regional politics impact who plays in the big game. Michigan was considered the #2 team in three out of four regions, but the South voted strongly in favor of Florida, pushing them up the poll.

We opened the Wolverines at -2 ½ (-105) but have taken twice as many wagers on USC as Michigan, causing the line to creep down. The sharps have mostly steered clear of this game to this point.

Florida +7 ½ -109 v. Ohio State

With a convincing win over Arkansas in the SEC title game, Florida edged out Michigan for the #2 spot in the BCS rankings by just 1/100th of a point. The computer rankings had the two teams tied, but Florida passed Michigan in the Harris Poll and USA Today poll. That was just enough for Florida to earn an invitation to the BCS National Championship Game.

We opened the Buckeyes at -7 (-105), and took a lot of early Ohio State money. The line spiked as high as -9, with twice as many bets on Ohio State as Florida, but a few sharps

by: Staci Richards - theSpread.com - Email Us

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