Another MLS season goes by, another MLS season schedule and playoff format is published...
The league released a new schedule and playoff format for the 2012 season during the run up to this year's MLS Cup. The 2012 season will see the return of the unbalanced schedule, while the playoff format will see an expansion of the home-and-away aggregate goals format into the conference finals. First, a few reactions to the new schedule and playoff format before I get into the impacts I see in qualifying for the latter.
The Changes in Format
MLS has gone to the long anticipated unbalanced schedule for 2012, and made the following statement explaining why:
“We have established a fair and compelling format for the 2012 season,” MLS executive vice president Nelson Rodriguez said in a statement. “This regular season will include more games between regional rivals and less total travel than we have seen in recent years. Because of the wide geographic distribution of MLS clubs, this structure should improve the quality of play, while continuing to give every club an equal chance of qualifying for the MLS Cup Playoffs.”I have long doubted the "travel = exhaustion" excuse in sports. It always seems intuitive, since jet lag affects most of us when we travel and we're not running for miles during each stop of our journey. It even makes more sense when MLS is compared to their European counterparts who all travel within countries the size of California or smaller when they play in their domestic leagues. However, when it comes to wins and losses the theory just doesn't pan out. Scorecasting did a great job of demonstrating that the vast majority of home wins can be explained by referee bias, and not fatigue due to team travel. Perhaps MLS would make the argument that the quality of play of both teams is poor due to so much travel, and that they're more concerned about the quality of the product on the pitch and less concerned about the home pitch advantage. Fair enough, although I don't think travel is the lowest hanging fruit when it comes to improving match quality. Rapid league expansion that has forced a dilution in the talent pool available to MLS clubs combined with continuing desires by players to join more prestigious leagues in Europe are likely the bigger culprit. Perhaps the league should take a breather from expansion, and let the league format stabilize for a while if they're so concerned about the quality of play.
This isn't to say that the league doesn't have a justifiable reason for taking this action, but let's just admit what it is about - money and setting up its future for more than 20 teams. Keeping cross country travel down means more savings for the owners, as does not expanding the regular season to the 36 matches required for a balanced schedule (although not adding matches may be hurting the national team). This is key in a league still trying to establish itself financially. Finally, if MLS really does desire to have more than 20 teams in the league and will avoid promotion and relegation like every other US professional sports league, there is simply no way to keep a balanced schedule when they reach that point.
So what is the impact of the regular season format? The biggest impact may be felt at the "regional rivalry" level that MLS seemed so concerned about. MLS strangely left Houston in the Eastern Conference, which means they will only face FC Dallas once per year and will be alternating the venue from year to year. Canadian clubs in the East (Montreal and Toronto) will only face Vancouver once as well. Yes, this isn't exactly local, but from what I am reading on line this presents a bit of a challenge for soccer fans in the north looking to better establish a vibrant, professional Canadian soccer community. For teams in the West who do remain in the Western conference, this arrangement presents a bit of a challenge for their local cup competitions. Given that Western Conference teams will play each other three times a season, one team will inherently have a home pitch advantage. That's not a very good format for a regional cup that relies on a balance in venues to minimize the effects of home pitch advantage. The new format will increase the number of local matches, but I don't know if the format will help the rivalries in the Western Conference.
I also suspect the Conference formats that rely upon three matches between each team will end up producing a bigger disparity in points distribution. This is due to the higher likelihood of better clubs taking advantage of an increased number of games against weaker clubs. Playing more games repeatedly against the same competition is a recipe for achieving the expected result over time rather than the upsets that can come with fewer matches. This will likely lead to increased disparity in points earned between the better and worse clubs. One also hopes that the league looks at the prior seasons' results to ensure teams from each conference get a balance of strong and weak opponents when playing in the interconference matches. A few years from now, when the 20th team is admitted to MLS, the disparity in the number of interconference matches played by each conference should disappear.
The changes to the playoff format have also provided a few new wrinkles. MLS has finally recognized that if they're going to go to the trouble of having a playoff, they need to provide some type of reward to the Supporter's Shield winners. Starting in 2012, the Supporter's Shield will host MLS Cup if they're able to make it that far.
The other major change - the expansion of the two-legged aggregate goal format to the Conference Finals - is not a good one. I've written plenty here and here about the penalty better teams who are involved in more competitions pay in such a format. Such a format makes sense for competitions such as Champions League where it may be the first time that season the clubs have met. It makes no sense as a playoff format that now can only include teams within a conference who have played each other three times already that season. The continued use and expansion of such a playoff format within MLS suggests to me that the league can't decide if it wants to cater to fans of European soccer or American professional sports. My contention is that if MLS is going to insist on a playoff format to determine its champion like other US sports leagues, it should use a single elimination format that rewards teams at the top of the table.
The Impact on Playoff Qualification
Regardless of the criticism, the playoff format is what it will be next season. With the changes that have been made, how are the odds of qualification impacted?
The challenge in analyzing MLS historical performance is the non-constant number of clubs in the league, the maximum number of points available, and the number of teams that qualify for the playoffs. Luckily, there is a method for translating historical table position data into a format that allows for comparison across seasons. Data from 2005 through 2011 was compiled for this analysis, with table position translated via the equation below and points earned converted to the percentage of total points available each season.
-LN[table position/(number of teams + 1 - table position)]
The transformed data was then plotted, and regression lines created along with the 50% prediction intervals (PI) associated with the data. Given the new playoff format and the lack of teams crossing over from one conference to the other for the playoffs, historical data was separated by conference. Plots for the Eastern and Western Conference data are shown below (click on graphs to enlarge them).
The fit of the regressions is relatively good - the Eastern Conference has an R-squared value of 0.80 and the Western Conference a value of 0.76. The main difference in those fit values can be attributed to the awful performances by Real Salt Lake and Chivas in 2005 where they earned 21% and 19% of the available points, respectively. Those data points are represented by the blue dots in the lower right hand end of the graph, just above the upper 50% PI line. If those two data points were removed, the R-squared value for the Western Conference would improve to 0.81.
An interesting comparison can be made between the conferences by examining the slope terms of the two regression lines (eg the number before the "x" variable). A higher slope term indicates that teams can achieve a particular table position with a lower percentage of points, while a lower slope term indicates that teams must earn a greater percentage of points to earn the same table position. To make the comparison easier, a plot of both conferences and their regression lines are shown below, along with a third plot of the regression line that would be associated with a single table of both Western and Eastern Conferences combined.
The graph demonstrates the difference between the two conferences. Looking at the right-hand side of the graph, once can see the separation between the upper table positions of the two conferences. The Western Conference line is lower than the Easter Conference line at those upper table positions, reflecting the difference in slope terms (10.0 versus 12.2, respectively). Based purely on the nominal regression line, one could argue that finishing at the top of the Western Conference is more difficult than accomplishing the same in the East.
Outcomes are never as deterministic as a single regression line suggests. Taking in to account the variation within the regression analysis, the reality is a bit murkier. The 50% PI lines quantify the expected outcome for the middle 50% of possible outcomes over time, which provides a way to quantify the expected variation over time. A similar interpretation is that 25% of the teams with a specific point total will finish above the upper dotted line, and 25% of the teams will finish below the lower dotted line. The regression study can also be flipped - points vs. table position - to produce 50% PI's for the point percentages required to finish in specific table positions. It is this relationship that is explored further.
Fifty percent of the teams finishing in the top position of a conference will earn between 56.9% (58 pts/1.71 PPM) and 62.8% (64 pts/1.88 PPM) of the available points in the East, while Western Conference teams will earn between 58.7% (60 pts/1.76 PPM) and 66.4% (68 pts/2.00 PPM) of the available points. It's certainly not a a statistically significant difference, but it is indicative of the mildly more difficult path to the top of the Western Conference.
Looking at the numbers close to a y-axis value of 0 helps identify the points required to simply qualify for the playoffs. The regression lines begin to overlap by the time they approach this y-axis value. Coincidentally, the single table regression line also overlaps the two conference lines at this point, suggesting that there is no real change in qualification odds via the league's move from using the overall 10th place finisher versus using the 5th place finisher from each conference. Utilizing the 50% PI data, the middle half of fifth place finishers in the East will earn between 43.0% (44 pts/1.30 PPM) and 48.7% (50 pts/1.47 PPM) of the available points, while those in the West will earn 42.3% (43 pts/1.26 PPM) and 49.7% (51 pts/1.5 PPM). The slightly wider variation seen in the Western Conference can be directly attributed to the slightly worse fit discussed earlier.
Interestingly enough, the data suggests it is completely reasonable to expect (via the 50% PI data) that teams with less than 50% of their available points could finish as high as the third playoff seed. Qualifying third would give the team a bye into the first proper round of the playoffs, avoiding the one game playoff required of the fourth and fifth seeds. If MLS got rid of qualifying the fifth team and simply qualified the top four for the playoffs, the 50% PI for percentage of available points in the East would be 45.5% (46 pts/1.35 PPM) to 51.2% (52 pts/1.53 PPM) in the West it would be 45.3% (46 pts/1.35 PPM) to 52.7% (54 pts/1.59 PPM). This would represent an increase of nearly 3% of available points, or an increase of nearly 3 points, to qualify for the MLS playoffs.
Conclusions
There is a good bit of historical precedent for teams earning less than 50% of the available points and making the MLS playoffs. Such an outcome is inherent to a league that qualifies more than 50% of the teams for such a playoff. Historically, 14 of the 28 teams that have qualified for the playoffs from the East have earned fewer than 50% of the available points, while 10 of the 30 teams that have qualified from the East have earned fewer than 50% of the available points. In both cases, the majority of these teams qualified in the 4th or 5th table positions. In the East, only four such teams have qualified as a third seed and only one in the second table position. In the West, four of the teams qualified as a third seed and two qualified in the second position. Such generous odds of playoff qualification shall continue until MLS admits a lower percentage of playoff participants via an increase in the number of teams in the league or reduces the number of playoff spots available.
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