Friday, 5 September 2014

Puckerings archive: Does Playoff Experience Matter? (30 Oct 2001)

What follows is a post from my old hockey analysis site (later It is reproduced here for posterity; bear in mind this writing is over a decade old and I may not even agree with it myself anymore. This post was originally published on October 30, 2001 and was updated on April 9, 2002.

Does playoff experience matter?
Copyright Iain Fyffe, 2002

We all have heard that playoff experience is critical for playoff success. It's certainly been said often enough. If a team, or rather the players on a team, don't have enough playoff experience, they don't have a prayer of winning in the post-season. I believe it's time we put this idea to the test.

The assertion is this: teams with more playoff experience will be more successful in the playoffs than teams with less playoff experience. We will define success in the playoffs as the winning of playoff series, not necessarily winning the Stanley Cup. We will test the assertion through head-to-head playoff series matchups. If the assertion is true, then a team's relative playoff experience should be a good predictor of the outcome of the playoff series.

To test this assertion, I used data from the past three NHL seasons: 1998/99, 1999/00, and 2000/01. I defined a team's playoff experience as the total career playoff games played in previous years by all players who played for the team in that playoff year. I then used these total playoff experience figures as the sole factor in predicting the winner of each playoff series. That is, I predicted that the team with more total playoff experience would win each series. Here are the results of these predictions:

 Year  Series  Right  Wrong  Pct
 1998/99  15  10  5  .667
 1999/00  15  11  4  .733
 2000/01  15  9  6  .600
 Total  45  30  15  .667

There you have it. Playoff experience is a very good predictor of playoff success, being right two-thirds of the time. But not so fast; we need to go deeper than this superficial analysis. The problem with this analysis is that a player's playoff experience is not independent of the quality of his team (defined here as regular season points). That is to say, a player's playoff success depends greatly upon him playing for a good regular-season team; but don't take my word for it.
We start with two simple points: (1) good teams generally stay good from year to year, while bad teams stay bad, and (2) teams retain a majority of the same players from year to year. Before I continue, let me demonstrate that these points are true.

To demonstrate the first point, I will simply use correlation. The following are the correlation coefficients for NHL teams' regular season points between 1998/99 and 1999/00, as well as the correlation for points between 1999/00 and 2000/01.

 Years  Correlation
 1998/99-1999/00  0.67
 1999/00-2000/01  0.77

As demonstrated in the above table, last year's points are an excellent predictor of this year's points. A correlation of 0.60 or more is considered high, and the relationship is therefore very strong.

The second point is also simple to demonstrate. I selected a random sample of five teams to test the stability of their rosters. I compiled the regular season games played in 2000/01 for players on each team at the end of the year who were also on the same team at the end of the previous year (1999/00). I then compared these results to the maximum number of man-games, which is 18 skaters plus one goalie times 82 games, or 1558 man-games. Here are the results:

 Team  Games  % of Max
 Atlanta  1086  70
 Los Angeles  915  59
 New Jersey  1300  83
 Phoenix  1002  64
 Toronto  1124  72
 Average  1085  70

As you can see, the team you play for this year is most likely the team you played for last year. On average, 70% of a team's games are played by players who also played on the team at the end of the previous year.

Now that I have established these points, let's move on to this question: how good a predictor of playoff success is regular season success? I again tested playoff series for the past three years, this time using regular season points as the sole predictor of series winners. The 'neithers' in the table below are the result of teams having equal points, and therefore no winner being predicted. The results:

 Year  Series  Right  Wrong  Neither  Pct
 1998/99  15  10  4  1  .700
 1999/00  15  11  4  0  .733
 2000/00  15  9  5  1  .633
 Total  45  30  13  2  .689

As you can see, regular season success is marginally better than playoff experience at predicting playoff winners. What this really shows is that playoff experience has no apparent effect on the results of the playoff. If playoff experience were important, it would be better at predicting winners than regular season points. However, they're virtually identical as predictors. The reason for this is that playoff experience is accumulated through playing for a good team. I have shown that players generally play for the same team from year to year, that good teams are generally good from year to year, and that good teams are successful in the playoffs. Therefore, players on good teams will accumulate large totals of playoff experience not by "knowing what it takes to win in the playoffs," but by playing for a good team that will tend naturally to win more, both in the regular season and in the playoffs.

The crucial point is this: playoff experience is the result of playing for a successful regular season team. Playoff experience is simply a reflection of playing for a good team. There is absolutely no evidence that having greater playoff experience will affect the result of a playoff series. If playoff experience were important, it would be better than regular-season points in predicting playoff series winners; in fact, it's marginally worse. In reality, it's the quality of the team that matters, not the playoff experience of the players.

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