We have often discussed the notion of "game state" on the pages of Sounder at Heart. Goals change games - they changes strategy, and for all the ambiguity of soccer statistics they often show that teams adjust play to meet their circumstances - just as we see on the field. On Wednesday, there were about 5 major changes in the game. The Sounders, in control, took the lead 1-0 after a favorable bounce to Brad Evans in the box. The defensive breakdown involved touches and movement from most of the offensive players on the field, along with an "unsuccessful" cross from Leo Gonzalez, taking the ball from Eddie Johnson on an overlapping run. Let's call that the first event.
27:56 Brad Evans goal
41:14 DeAndre Yedlin injury
48:07 (45:00) Halftime
84:56 Michael Gspurning red card
92:22 Eddie Johnson goal
Fortunately, for analytical purposes Yedlin's injury coincided more or less with the half, and nothing particularly significant happened between Gspurning's send-off and EJ sealing the game. I am mainly concerned with Evans' goal and with Yedlin's departure at the half, and what these events did to the game.
The above plots are generated by measuring team performance in a 10-minute sliding window, gathered at 5 minute intervals through the game. This results in a certain amount of double counting, so the values should be considered "rates" (i.e., don't try to sum them up to match the full-game total). The first vertical dashed line from the left marks Evans' goal. The second marks Yedlin's injury. The stats should be mostly self-explanatory (however, note that accuracy excludes crosses and throw-ins while passing attempts does not), with the exception of "Clearance Bias (Clearances/(Tackles Won + Interceptions + Recoveries) which I'm using as a proxy for whether the defense is simply interfering with the opponent or redirecting play to the offense.
The shift to the diamond midfield was a success for the Sounders on Wednesday. After a high-energy and high-turnover start to the game, the team settled into passing Colorado off the pitch, largely due to outstanding possession work among Evans, Osvaldo Alonso, Clint Dempsey, and Eddie Johnson. The team completed 76% of its basic passes and generated 3 shots on goal from the start of the game to Evans' goal. I was not likely the only fan saying, at the time, "don't let up on the pressure." Seattle didn't - at least not completely, completing 77.6% of basic passes for the remainder of the half, but generating only 1 additional off-target shot.
The Jekyll and Hyde nature of the Sounders halves must be a concern. With DeAndre Yedlin unable to continue, Marc Burch slipped into the midfield, Adam Moffat shifted to the right, and Evans moved to fullback. The only shot on target Seattle registered for the remainder of the game was Eddie Johnson's stoppage-time clincher.
One could argue that the Sounders shifted tactics to protect their lead, or that Colorado changed their approach at halftime. The clearance bias graph certainly suggests this happened at the very end of the first half, playing with 10 men due to Yedlin's ankle. One could even blame fatigue, to a degree. However, playing a similar formation with a similar volume of pass attempts, opportunities dropped significantly in the second half. I attribute this, in part, to Moffat's increased responsibility in the central midfield, Evans' relative absence from the attack, and Burch's unfamiliarity with the role - an argument supported by the numbers on passing accuracy. The formation and personnel in the game were simply unable to maintain the numbers from the fist 45' that made scoring so inevitable
If Yedlin is unable to play in the first leg against Portland, the diamond midfield may not be an option. The Sounders' performance of the first half may be enough to advance (although improved finishing would help them along). The performance from the second half against Colorado would likely not be good enough.