HSAC’s 2019 Stanley Cup Playoff Predictions

By Andrew Puopolo

Tonight, the Stanley Cup Playoffs begin when the Columbus Blue Jackets head to Florida to take on the President’s trophy winners Tampa Bay Lightning. The Lightning are heavy favorites to win the Stanley Cup this season, having finished with 21 points more than the team with the second best team in the league. In light of their dominance, how likely are the Lightning to win the Stanley Cup this season?

To answer this question, I used a Glicko rating system model to simulate this year’s Stanley Cup Playoffs 100,000 times. For those who are unfamiliar with what the Glicko rating system is, the Glicko rating system is an extension on the well known Elo rating system that dynamically updates after games. If a team wins a game, their rating goes up, if they lose a game their rating goes down. Beating a good team makes your rating go up by more than beating a bad team.

What differentiates the Glicko system from the Elo system is its ability to incorporate timing of matches into its prediction. In the Elo system, the rating changes at the same rate at the beginning and end of the season, which is problematic as the summer offseason changes the strengths of teams considerably, which should be reflected by team’s ratings moving more at the beginning of the season.

We fit our Glicko model using game results from the 2005/6 to the 2017/18 seasons. For the technical details behind fitting this model, please email me at andrewpuopolo@college.harvard.edu.

In our Glicko model, we estimated that the home team has an advantage of 33 rating points per game. This means that if two evenly rated teams face off, then the home team has a 54.7% chance of winning the game.

Our simulations are run “hot”, which means that we are constantly updating our estimate for a team’s strength throughout the (simulated) playoffs as they advance through more rounds.

First, we will look at our predictions for the first round of this year’s Stanley Cup Playoffs:

These predictions are pretty much more or less what we expected. In the Eastern Conference, the 1-4 matchups in each division (Tampa Bay vs Columbus and Washington vs Carolina) see the team with home ice advantage as heavy favorites. We also have the Boston Bruins as slight favorites over the Toronto Maple Leafs. However, it is interesting to note that the Islanders are underdogs against the Pittsburgh Penguins, despite having home ice advantage. This is due to the Penguins having a rating that is 34 points higher than the Islanders, as it incorporates some of last year’s results into the estimate for a team’s rating.

In the West, the predictions for this series are more of a toss up. The Sharks and Golden Knights have almost identical team ratings and the model gives San Jose a slight edge due to home ice advantage. There is a similar phenomenon in the Winnipeg vs St. Louis series. The other two series see the better team with about a ⅔ chances of advancing.

Next, we will take a look at our predictions for the winner of each Conference

The Lightning are overwhelming favorites in the Eastern Conference, but despite their regular season dominance, only make it to the Stanley Cup Finals in 38% of our simulations. This is a testament to the great parity of hockey. Another thing to note is that despite having the second best record in the Eastern Conference, the Bruins only make the the Stanley Cup in 12% of simulations, while the Washington Capitals who finished with three fewer points in the regular season make the Stanley Cup in 20%. There are two explanations for this. The first is that the Capitals are rated higher than the Bruins due to their Stanley Cup win last season. The second is that there is a higher probability that the Bruins face the Lightning en route to the Stanley Cup than the Capitals do. The Bruins have to face the Lightning in 78% of simulations, while the Capitals only have to face the Lightning in 55%. In addition, the Bruins have to face a tougher opponent in the first round than the Capitals do.

The Western Conference is much more even than the East. Only two teams (the Dallas Stars and Colorado Avalanche) have a fewer than 10% chance of qualifying, while no team has higher than a 21% chance. This shows the incredible parity that is currently present in the Western Conference.

Finally, we will look at our predictions for the probability of all sixteen teams winning the Stanley Cup:

Predictions for Stanley Cup Champion

Our results are somewhat as expected. The Lightning have a 27% chance of winning the Stanley Cup, while we see pretty strong parity across the rest of the league. We see that the East has about a 60% chance of winning the Stanley Cup over the West, which makes sense given that 3 of the top 4 teams by record came from the East.

If you have any questions for Andrew, please reach out to him at andrewpuopolo@college.harvard.edu

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