Round 17 Predictions

Stupid Thursday game caught me out again. Will update when I get a chance.

round17

UPDATE I’ve now added in the match importance ratings for each game. By far the most important game was the Thursday night epic between Hawthorn and Sydney. I’ll write a bit more about that in the review but that match had approximately a 40 percentage point change in top 4 chances for each team.

The next most important involves Port Adelaide and North Melbourne, the two sides sitting in 8th and 9th. While North are much better chances to stay in the 8, a loss to Port this week sees those chances shift further into Port Adelaide favour, with a ~25 percentage point swing either way based on the match.

importance_R16

importance_table_R16

Round 16 Predictions

As our ELO model suggests, the top 8 is super tight. In fact, our simulations have a really tough time separating out clear favourites in our top 8 race. Data from The Arc, suggests that this is the tightest race we’ve ever had at this stage of the year. Considering that, anytime two top 8 teams play each other, its going to be important.

round16

We’ve got 2 top 8 clashes this week in Sydney v Geelong and WCE v North, which have big implications for the respective finishing positions of those teams. In fact, in the very short life of our Match Importance rating, the Sydney v Geelong clash is the most important game of the season.

importance_R15The three most important matches are below:

Port Adelaide v Hawthorn, Thurs 7:20pm Adelaide Oval

The other super important match is this clash between 1st and 9th. Hawthorn is sitting pretty at the top of a very congested ladder while Port remains our best chance to jump into the top 8 according to our match simulations. The difference in a win or a loss for their top 8 chances is ~28%, so a win goes a long way to them making the leap. Hawks superior rating gives them the upper hand but HGA brings Port into it. Hawks by 5 points. 

Geelong v Sydney, Fri 7:50pm Skilled Stadium

The clash between 2 of the premiership favourites according the bookies, our model has this as the most important match of the year so far (at least since I’ve been doing importance rankings). The percentage change in top 4 chances from a win or a loss is 36.5 for Sydney and 38.4 for Geelong! Our model gives Geelong the slight edge in ranking points, as the 3rd best team, while Sydney dropped slightly back to 5th after last weeks loss. The HGA gets Geelong a bit more of a bump.  Geelong by 12 points. 

WCE v NM, Sun 1:20pm Domain Stadium

Given how tight the top 8 is, this has big implications on the makeup of the bottom part of the 8. Both these teams are at most risk of dropping out of the 8. A loss here puts them behind the pack for top 4 and at risk of a rampaging finish by Port Adelaide. WCE are rated about 30 rating points better, with the home ground advantage. Eagles by 15 points. 

Round 15 Predictions

I’ve been caught out by the Thursday game so I won’t have a chance to write a preview until tomorrow. Here are the predictions anyway!

UPDATE: So I’ve got around to taking a bit of a closer look at this rounds matches.

round15

Finally we reach our last bye round – I know I’m looking forward to getting to a full round of matches. There are a few tight matches according to our ELO model, however the tight matches all appear pretty meaningless according to our Match Importance metric.

Round15MatchImportance

By far and away the most important match this round is the Syd v WB match – having big implications for both teams top 4 chances. I had a nice discussion this week with @Matterofstats on twitter about that measure – he suggested trying to weight the value of importance based on the likelihood of it occurring. I hope to implement that this week but I encourage anyone to jump on and have a read of his methodology.

Round 14 Predictions

Our next bye round, subjectively, doesn’t look great on paper. Only the Collingwood v Freo match is considered tight by our ELO model, however it is fairly insignificant as measured by our Match Importance metric. The remaining matches, despite having some significance on the relevant team finishing positions, look fairly one sided.

round14

Adelaide v North Melbourne, Thurs 7:20pm Adelaide Oval

Probably the most interesting match of the round, and certainly with the biggest Match Importance rating, we see the top rated Crows favoured pretty heavily over the 7th ranked Kangaroos, particularly with the Home Ground Advantage. A loss for either side affects their top 4 chances by roughly 30%. Adelaide by 23 points. 

Collingwood v Fremantle, Fri 7:30pm MCG

As indicated, this match doesn’t really have an effect on our final finishing positions for either team, giving a combined change in probability of the top 8 of 2.8% for both teams. Despite that, the game looks like it could be tight, with our 9th ranked Freo team on the up after a tough start. Freo by 5 points. 

Round 13 Predictions

The first bye round of the year presents us with two groups of games – coin flip’s in the North/Hawks, Freo/Port and Bulldogs/Geelong games, while the others the ELO model expects to be relative blowouts. You’ll also notice that I’ve added ‘match importance’ to the table below, which you can read about in my recent blog post.
round13

I’ll summarise some of the important games below.

Round13MatchImportance

North Melbourne v Hawthorn, Fri 7:40pm Etihad Stadium

My model, as I keep harping on about, is still unimpressed by North Melbourne, rating them as the 8th best team and having them finish 7th on a (tightly packed) simulated season ladder. The Hawks on the other hand sit in 2nd in our ELO ratings. The system gives North a bit of a bump for being the home team. Our model is also naive to player selection so it doesn’t care about the Kangas injuries! Hawks by 5 points. 

Fremantle v Port Adelaide, Sat 3:35pm Domain Stadium

Freo, despite their awful start to the season, has been steadily improving their ELO rating and currently sit just behind Port Adelaide on the ELO ladder. They get a decent bump for their home ground but a relatively impressive Port team just gets the nod. Port by 7 points. 

Bulldogs v Geelong, Sat 7:25pm Edihad Stadium

Possibly the game of the round – certainly the most important by our new importance rating! Two teams with almost identical ELO ratings – the Bulldogs get a bump with the notional Home ground. Has some big implications for each teams final ladder positions, roughly reducing the losers chance of a top 4 spot by 35%! Bulldogs by 7 

Round 12 Predictions

Last week was a great week for our model, tipping all 9 games correctly! Onto this weeks set of games and it looks like a tough round to tip! There are a bunch of games that are difficult to seperate by bookmakers and also by my ELO model.

round12

 

Port Adelaide v Western Bulldogs, Sat 1:30pm Adelaide Oval

This game is setup to be super close – Port Adelaide have been surging in the last couple of weeks, bridging the originally wide chasm between 8th and 9th place. After gaining a whopping 28 ELO points last week, they enter this game as slight favourites due to the Home Ground Advantage. Port by 3 points. 

Geelong v North Melbourne, Sat 7:25pm Etihad Stadium

My model continues to be unimpressed by North Melbourne, despite having the Xth best start to a season in the history of the AFL, currently rating them as 8th best side. Geelong’s recent mishaps against Collingwood and Carlton however were treated rather harshly by the ELO model, seeing them slip from the 2nd best to 7th best team. The two teams are almost identical in ratings, with Geelong getting a slight bump due to HGA. Geelong by 9 points. 

West Coast v Adelaide, Sat 7:40pm Domain Stadium

Adelaide this week became the first team to topple Hawthorn as the top ranked team since 2014, however go into this one as slight underdogs due to playing away against the 4th best team by our ELO ratings. Could be the game of the round. West Coast by 5 points. 

GWS v Sydney, Sun 4:40pm Spotless Stadium

Even taking away the subplot of big brother versus little brother, the ‘battle of the bridge‘ promises to be a tight matchup between the 5th (GWS) and 3rd (Sydney) best teams in our ratings. HGA gives GWS the slight edge according to our model. GWS by 4 points. 

Even games like Melbourne v Collingwood and St Kilda v Carlton promise to be close – my model is perhaps operating the home team chances here due to applying a flat home ground advantage, despite one probably not existing in these Melbourne based games 1. The only real confidence that my model has appears to be losses for the 3 worst sides in my ratings system (Essendon 20%, Brisbane 37% and Gold Coast 31%).

 

round12to23

Notes:

  1. something I’d like to fix

Round 11 Predictions

I’ve separated out the simulations and ratings update into another post and I’ll just focus on this weeks games here.

Last week gave my ELO model a 4-peat of 6 out 9 tipping weeks. There were quite a few close tips this week, with an MAE of 23, bringing our season total to 64 (71%) with an MAE of 30.6.

round11

To this weeks games, we see some tight matchups. Concretely, Geelong v GWS gives Geelong a slight edge with Home Ground Advantage. Similarly, the Bulldogs are tipped to slightly get up over WCE despite being rating below them due to being the home team. In our closest matchup, the away Port are expected to just get over Collingwood in a coin flip.

Pre Round 11 Ratings

The congestion at the top of our ELO rankings still remains, although ‘the challengers’ to the top 4 may be slightly sorting themselves out. Only 9 rating points separate the top team (Hawthorn, still!) and our 4th team (tied between WCE and Adelaide) which is within the Home Ground Advantage we apply to the home team of 30 rankings points. After that, Geelong is in a bit of freefall, losing 45 ratings points (roughly the equivalent of a margin of 10 points) and 6 spots in our ranking system in the last 2 weeks! North Melbourne continue to be unimpressed by our model despite their 10-1 record.

ELO_preR11

For another week, we get a new leader in our season simulations! Sydney has continued their impressive form this year and their current record, along with being the 2nd highest rated team, gives them the edge at the top of the ladder. In fact, they are become closer to being certainties to make the 8 and figure in the top 4 in 2 of every 3 simulations.

round11to23

In our weekly discussion on the fight for a new member of the top 8, Port Adelaides win on the weekend keeps them in the race, with 34% of simulations seeing them entering the top 8. Nonetheless, the likelihood is that our top 8 is already set.

simDistR11

Round 10 Predictions

For the third week in a row, my ELO model managed 6 correct tips, with an MAE of 29, bringing our season total to 58 (72%) with an MAE of 31.5.

This upcoming weekend shows us a few close matches that are difficult to call. Our current ELO rankings show us that there is more congestion at the top of the ladder, with a clump of 6 teams forming, with the Bulldogs and North (still!) just outside of that. We again have a decent drop-off after this top 8, suggesting that making the finals from here might be tricky for those bottom teams.

ELO_preR10

Onto this weeks predictions, and there are a few tricky games to pick. Unfortunately, the only game between our top 6 clump of teams is Adelaide v GWS with our model given the Crows a slight advantage at home. The model also expects tight tussles between StK and Fremantle, essentially tipping a tie (it gives Freo a 50.1% chance of winning) and struggling to seperate Melbourne and PA.

The biggest round of the match, in terms of media coverage, is certainly Sydney v North Melbourne, given that the Kangaroos are still undefeated. Our model is giving the Kangaroos only a 39% chance of extending their start to the season to 10 wins, which would give them the equal 9th best start to a season in AFL history.

round10

Simulating the season gives us a new leader on the top of our predictions – GWS! Our models sees them finish on top in 17% of simulations, just above a group of 4 teams (Geelong, Sydney, North Melbourne and Hawthorn) on 16%. Certainly that log jam at the top is difficult to seperate this far out.

simTable

Another interesting pattern is solidifying, where we see a really big split after the top 8. Again, as our ratings suggest, there is a big gulf between those top 8 teams and we don’t give them bottom teams a very big chance of moving up into that top 8. Melbourne (26%) and Port Adelaide (24%) are still the biggest chances.

round10Dist

Round 9 predictions

Last weekend we again managed 6 correct tips, with an MAE of 33.9, bringing our season total to 52 (72%) with an MAE of 31.8. I’m hoping from here on in, we can maintain greater than 70% tipping and get the MAE under the 30 point mark 1

Onto this weekend, it looks like there are two standout games in the Hawks v Swans and the GWS v WB matchup. All 4 teams in our congested top 8, with the Hawks rated slightly higher, and at home, while the home ground advantage giving the Giants a slight edge over WB.

 

round9b

Our ELO ratings again show our clear separation of the Top 8 that we observed last week. This is providing more evidence to the idea that the Top 8 is already set by this point in the year. It also seems like we have a decent drop-off after about 13th, with not a lot to separate at least the bottom 4 (or maybe 5) teams. I’ll continue to monitor these groupings as the year goes on.

It is also interesting that the model still doesn’t rate North Melbourne either! Despite this, we give them a very good chance to improve their winning start to the season over Carlton (76% chance) – you can review the analyses of how good that start is here.

ELO_preR9

Simulating the rest of the season shows us again that we are relatively confident that the top 8 is already set, with only Port Adelaide (32%) and Melbourne (24%) making the 8 from outside with any regularity. While our model is is giving Geelong and Hawthorn >70% chance of clinching top 4, it has trouble picking the other teams, with essentially an even spread for the remainder of teams 3rd to 7th.

North Melbourne still sits at a predicted 3rd, despite ranking 8th on our ELO rankings. Those banked early wins are important.
R8to23

I’ve also shown the distribution of wins for each team, with the columns representing groups of 6. Hopefully this shows a little bit that, rather than predicting Geelong to get exactly 16 wins, that is the mean number of wins in our simulations, with a distribution around that number.

round9to23
It also, I think, graphically represents the idea that, we don’t think we will have two teams on 16 wins, with 6 teams following on 14 wins, but rather that the mean represents the relative confidence we have in that team finishing higher than another team. In fact, if Geelong ends up on 16 wins, it probably won’t even finish 1st, given the high distribution of teams other than Geelong it in the region above 16 wins. I might explore this concept further in a later post but I’ll start to include this plot.

Notes:

  1. I already have some thoughts on improvements of the ELO rating system