The Illusion of Safety: Sounders can't rely on their Shield-winning formula

"This isn't the Wild West!... The wild west wasn't even the Wild West!" - John Spartan (played by Sylvester Stallone in Demolition Man)

Commentators often unsurprisingly begin the discussion of Seattle's expected 2015 performance from a Supporters' Shield baseline. It is not exactly the same team - replacing two starters across the backline. The squad is a year older; adjusting for positional differences, the projected 10 starting outfield players exceed the average playing age in MLS by an average of roughly 3.5 years. However, only Leo Gonzalez and Gonzalo Pineda are so far past peak as to expect significant age-related decline. Brad Evans' move to center back represents an effort to stabilize and improve Seattle's weakest position from 2014, and may increase the use of a very effective Lamar Neagle/Marco Pappa wide midfield pairing. The most significant obstacle to Shield contention in 2015 may not be the modest changes of the offseason, but instead be natural changes in fortune.

The definition of insanity is doing the same thing and expecting the same result. Such is not the traditional aphorism, but I think my modified version is particularly appropriate for sport analysis. The result of a competition is rarely defined by either individual or team performance. In every 90-minute soccer game, there are 11+3 opposing players who may perform differently, a coach who my make different decisions, and a referee who may blow the whistle too often... or not enough. A Clint Dempsey goal from 2014 could be parried by a 2015 goalkeeper or kick-saved off the line by an opportunistic defender. For the sake of discussion, let's define "luck" and "fortune" as those aspects of the game that are beyond the team's direct control, and make some effort to qualitatively measure their impact on last year's performance. Two specific permutations of Lady Luck clearly sided with Seattle:

Goal Distribution

Teams will adjust their tactics to chase a result - throwing players forward to score or pulling into a bunker to tighten the defense... but there's little evidence to suggest any MLS squad is exceptionally skilled at choosing when goals are scored (see, for example, sidereal's excellent analysis of bunkering tactics). The figure above depicts ppg vs. goal differential for all MLS teams over the past 10 years of play. The relationship is predictably strong - but teams rarely exhibit consistent trends from year to year (i.e. if some teams were better than others at scoring to chase a result, we might expect them to consistently receive higher point totals for a given goal differential by efficiently distributing their scoring tendencies). Taking an extreme example, Chivas USA has both the best (2014) and the worst (2011) return on GD of the past 10 years. The linear trendline may be used to calculate an expected point total for a given GD. The LA Galaxy have exhibited greater than 6 point year-to-year fluctuations of performance relative to the trendline. There does not appear to be any robust "skill" involved in outperforming GD, so it may be used as a shorthand measure of how opportunistically goals have been distributed. In 2014, Seattle outperformed the 10-year average by 6.62 points (second in the league, behind Chivas). The six years Sounders have been in MLS are shown above in green: 6.62 is their highest mark, 2013's 5.63 comes in second, and 2012's low of -3.38 would have easily lost the Shield had it come 2 years later.

Health

Chad Marshall - a center back with a history of concussion issues - missed only 3 games en route to the Defender of the Year award in his first season for Seattle, and the Sounders earned only 1 point from those games. The team lost the only 2014 regular season game missing Osvaldo Alonso - and now begin 2015 without him. These are anecdotal reasons both to observe that Seattle was lucky with 2014 player availability and also to fear injuries at key positions. Just how healthy were they? Here's a measure of Seattle's lineup usage in MLS:

"#players" is the total number of Sounders who received at least 1 minute on the field in MLS regular season play. "Top11" and "Top18" are the share (%) of playing minutes for the team accounted for by the top 11 players and top 18 players on the roster, respectively. Leo Gonzalez, at 1,836 minutes, ranks 11th on the squad and is the only regular to miss substantial time to physical problems. In a season in which the team used a three-player rotation for two midfield positions, a de facto three-player rotation for the second cb slot, and lost two starters to regular national team duty, Seattle exhibited its second most constrained roster for playing time (trailing only expansion, 2009). Some of this data may be attributed to managerial discretion, but we can also compare the three indices above to other MLS teams. Seattle's 24 players used in 2014 is tied (with Houston) for lowest in the league, Top11 is a close second (to LA's 77.77), and Top18 is first in MLS. MLS average for the 3 indices is 27.4, 72.36, and 92.91, respectively. Insofar as playing time represents player availability, Seattle's 2014 was exceptionally healthy compared to both MLS average and its own team history. We should expect 2015 to be different, and we should remember that lineup changes have a measurable impact on results:

Seattle won 8 of its 10 games in 2014 in which it changed out 1 or fewer starters between games. On a broader, MLS-wide scale in 2014, lineup consistency has a similar impact on results:

This sort of work presents a significant the-chicken-or-the-egg problem. Teams that fail to perform will modify the lineup for the sake of change, and teams that succeed tend to avoid modifying a working system. Nevertheless, if people are interested in reading up on this sort of trend more deeply, I recommend sidereal's analysis from 2013 as well as Jared Young's recent article at americansocceranalysis.com.

Taking the measure of a team may amount to more or less than the sum of its players over a season or across 90 minutes. Seattle needs a clear plan to win with some of the Sounders they had but also - more importantly - a plan to win with the Sounders we are given.