Quantifying Home Field Advantage: Adjusting and Exploiting Implied Team Totals
Everyone knows that Drew Brees and Big Ben have significant home/away splits for fantasy football and their actual performance. Why is that?
Ross Tucker (@RossTuckerNFL) wrote an Article in early January on why he thinks, as a former NFL player, that home field advantage comes into play. He cites crowd noise, energy, and familiarity as the three main reasons players perform better at home than on the road. I would highly recommend reading the article as he dives deeper into how those three variable affect players.
The three variables Tucker talks about don’t affect just QB’s though. Seattle as a team was AWFUL on the road last year. Seattle’s offense averaged 28.38 points at home last year, but couldn’t muster more than 15.88 PPG on the road. Some Seattle road game highlights was only scoring 10 points against the Packers, 3 points against the Rams, 6 points against the Cardinals and 5 points against the Bucs. While their offense was atrocious on the road, Seattle’s defense wasn’t substantially worse only letting up an extra 2.5 points. Looking at their win percentages, Seattle won 88% of games at home and only 38% on the road. Yikes.
The large home/away splits for teams like Seattle sparked the idea to try and quantify each team’s home field advantage and how predictive it could be for future games especially with totals. Currently, Odds-makers generalize that a team should be given about a three point advantage when at home in addition to whatever the spread would normally be. Yet some teams are substantially more volatile than three points given their location. I started producing excel sheets each week that look at Home/Away points per game, Vegas totals, and implied team totals to visualize this. For example, here's the sheet from week 16:
In a nutshell, it breaks down Vegas lines into implied team totals and their Points Per Game scored and allowed based on being at home or away:
Going more in depth we’ll use Miami as an example:
Implied: This is how much Vegas expects this team to score (18.75).
PPGF (Points per game for): How much a team scores on average depending on home or away (18 PPG on average on the road).
PPGA (Points per game allowed): How much a team allows on average depending on home or away (21.4 allowed on average on the road).
Adjusted Implied: A formula using a team’s implied team total, PPGF and the opposing teams PPGA. (According to this adjustment Miami is expected to score 20.5 points)
ADJ-IMPLIED (Adjusted subtracted by Implied): How much the formula expects a team to score subtracted by their implied Vegas total (The formula expects Miami to outscore their Vegas total by 1.7 points).
Vegas Total: The total amount of points Vegas expects to be scored in the game between both teams (42).
Adjusted Total: The total amount of points the formula expects to be scored in this game between both teams (45.6).
ADJ-V Total (Adjusted total-Vegas Total): How many points the formula expects to score subtracted by how many points Vegas expects. (The formula expects 3.6 more points scored in this game than what Vegas suggests).
If you don’t remember this game against the Bills, 65 total points was scored. This means my adjusted total was more accurate than Vegas’.
Why was it more accurate though? What kind of actionable analysis can these sheets produce? For the Buffalo-Miami game, you see that Buffalo scored 30.7 points on average in home games (very high). You can also see that Buffalo’s defense is actually not great at home, allowing 24.7 points on average. They tended to get in shootouts when playing at home. Combine this with a Miami team that wasn’t affected much by playing on the road and you get a total that is likely to go over.
“You can’t use one game as a sample for a whole season, Matrix. That’s ridiculous”- everyone everywhere.
Well, I spent WAY too much time going through every game since week seven of last season and compiled some results.
Further Explanation:
If you aren’t familiar with Vegas totals and betting, people make a living off hitting 55% and above. This system would have hit 61% if you bet every game of the NFL season. That’s pretty much unheard of. Now if you only bet games where my system suggests the total will be either three more or less than the Vegas total you would have won 70% of the time.
I wanted to break it down further, so I looked at how each team's adjusted team total performed against their implied team total. Helping to answer the question, were the totals just lucky or legit? Winning 61% overall and 63% above a small threshold shows me that this wasn’t just luck.
Another way to analyze these numbers is to see if both teams are trending in the right direction. For example, Miami was expected to score 1.7 points more than expected and Buffalo was expected to score 1.9 points more than expected. This means that both teams are trending to outscore their implied team total. Looking at those numbers, it once again hit at an outrageous number (68%).
Before you think I’m a lunatic, I don’t expect these numbers to continue at this rate year to year. However, I do expect it to stay above 55%. This means that this system can be a valuable tool for not only bettors but DFS and fantasy football players as well. If I can accurately project a total better than Vegas, it is yet another piece of the puzzle that gives you a leg up on your competition. There are some concerning flaws with the system like strength of schedule, injuries, in-season coaching changes as well as the sheer simplicity of it. That’s what is kind of great about this system though. It’s not like you have to bet/use a player in any game if there are major red flags. Last year against the Jaguars the Broncos had to start Paxton Lynch instead of Trevor Siemian. The system suggested the over based on previous numbers but anyone with half a brain knows not to bank on an over with a rookie’s first career start.
How to apply this to your different areas of degeneracy and why it matters:
DFS & Season Long
Warren Sharp (@SharpFootball) wrote an Article about how hitting the over in a game is actually more meaningful to fantasy points than having a high Vegas total. Players score more fantasy points in games where it goes over the Vegas total than in high total games themselves. This could be extremely useful for DFS players attempting to stay ahead of their competition. If you can identify which games have a good chance at hitting the over, you have a better chance at picking under the radar players with blowup potential as well as seeing which games you should potentially avoid. This system can also help season-long players decide between two Quarterbacks of similar weekly ranks.
Betting
If I keep hitting at this clip, it’s pretty obvious you should start to tail the system. If year to year this system ends up not being profitable at the worst, it can help give you a better idea of home field advantage and which teams to avoid on the road.
I will be tweeting out a sheet with all of this information each week of the season as well as writing up my analysis on important games.
If you would like to see all of the results week by week from last season or want more info feel free to email me at fantasyfootballmatrix@gmail.com or DM me on twitter @Fantasy_Matrix.
