Round 15 sees the last week of the bye period play out and I have no doubt that footy fans everywhere will be eager to get back into 9 games a week. This round is not quiet as dour as the last, but there are still only two games that will likely have any significant bearing on the final 8 this year; Sydney v Western Bulldogs and Melbourne v Adelaide.
The market rates the implied probabilities for each of these games, as well as the Carlton v Collingwood clash, to be about the same as the FFSS system rates them. This means that for those who have come here looking to bet on one of those games, the best advice I can offer you is, hold onto your money.
The "blockbuster"1 tonight between West Coast and Essendon of course may have some top-8 implications if the Bombers can cause an upset, but FFSS puts the probability of that happening around 6% thanks to a big HGA and a sizable difference in class. However, it should be noted that the bookies have Essendon as implied 5%, so there may be a tiny tiny smidgen of value there for a madman.
My usual qualifiers about using model predictions for betting apply.2
The graphic above highlights all of FFSS's probability estimates for the week. The prices next to each team are the minimum suggested price to take if you were to bet on them to win the match, assuming that FFSS predictions are perfect. In reality this is, of course, very likely not so.
The graphic opposite shows the FFSS team ratings at the start of the round. These, along with a concession for Home Ground Advantage are the direct inputs for the final probability estimates.
Rather then write previews for every match of the week, I will instead comment on interesting discrepancies between bookie odds and FFSS odds, why these may exist, and whether there is any value in betting at the available price.
Gold Coast v St Kilda
In a week where markets seem so well calibrated with FFSS predictions, this game certainly stands out. The markets have the, appearingly slightly rejuvinated, Suns as favourites at home, while FFSS does not think that home ground advantage will be enough to make up the difference in class between the middle-of-the-pack Saints and cellar dwellers Gold Coast.
The difference between public and model perception is most likely due to the Suns slightly more encouraging performances in their losses to Hawthorn last week and Richmond the week before their bye. As these were still losses, they haven't gained anything in FFSS's eyes.3
The model currently has the Saints as 64% chances of winning, while some bookies are currently offering implied win chances of 48%. Even considering the possibly inefficiencies of the rating system, I'd still say a bet on the Saints, in an otherwise lean week, offers pretty good value.
Bet 3 units on St Kilda @ 2.08 - Palmerbet
- I wish there was a sarcastic air quotes key on my keyboard
- I have translated my calculated probabilities into inferred match odds and compared these to the current prices offered by some of the bigger bookmakers around the country, highlighting any major discrepancies. The reason I have done this is not to recommend or even advocate having a bet on any particular team (although I will certainly talk about "good bets" and "value"). But it is rather used as a way to explore the strengths and weaknesses of the model in greater detail.
Bookie prices can be seen as a general "public consensus" about what the true probabilities of a team winning a match are. When the model differs greatly from the public view it is good to know why. Is it seeing something else that the public are not valuing? Or, is it missing something entirely that others are taking into account? If it's the latter, then there is clear improvement that can be made, if the former, then I guess we're on to a winner. All betting amounts will be discussed as unit bets assuming you have 100 units to play with as your full bankroll. For example if you have $1000 that you're willing to lose over the year if worst comes to worst, then 1 unit is $10. A higher unit bet shows more confidence in the models assessment and the value to be made.
- They certainly haven't lost as many points as they would have, had they played poorly, but the way the FFSS system is set up, a team only gains ratings points by winning. This system will change at some point, but it requires a big overhaul and most likely won't be until the off-season.