Wednesday, October 30, 2013

Defensive Metrics and the 2013 Seattle Sounders

This article originally appeared in Sounder at Heart

With 13 goals conceded in their past five games,  a fair bit of blame for the late season collapse of Seattle would seem to lie with the defense.  While the Sounders boast a talented strikeforce, the team has struggled all year to consistently create opportunities.  Much of the success of the team is due to the defense, although this excellent Zach Slaton piece finds inadequacies all over the field.  Despite the recent dip in form, there is plenty of reason to believe the Sounders defense can rebound.
The above graph shows every team in MLS' history shots per game plotted against goals per game.  Unsurprisingly, there is a relationship.  Ok, so we generally know the less shots you give up the less goals you give up.  But what are the underlying defensive indicators that can predict fewer chances allowed?  And how do the 2013 Sounders stack up?
It turns out that defensive aerials won explains nearly half the variance in shots conceded.  The Sounders have done a good job all year in the air defensively, and are fourth in the league in this metric, just behind the LA Galaxy.  Another metric that Seattle scores well in is PAPPA (Passes Allowed Per Pressing Action), which is adapted from Colin Trainor's introduction to defensive metrics. A pressing action is defined as: tackles won + interceptions won + defensive aerials won.  The lower the number, the better.
1Sporting Kansas City5.7
2Seattle Sounders FC7.2
3Portland Timbers7.6
4Real Salt Lake7.7
5Columbus Crew8.3
6San Jose Earthquakes8.5
7Houston Dynamo8.6
8FC Dallas8.6
9Toronto FC8.7
10L.A. Galaxy8.7
11Montreal Impact8.8
12Colorado Rapids8.8
13Vancouver Whitecaps8.8
14Philadelphia Union8.9
15DC United8.9
16Chicago Fire9.0
17New England Rev.9.3
18New York Red Bulls9.3
19CD Chivas USA9.7
PAPPA also explains a fair amount of the variance in shots conceded (though less than defensive aerials won).
Seattle has proven this year that, when playing aggressive and intelligent defense, they are one of the most difficult teams to break down.  Tonight would be a good time to get that mojo back

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