When Stefan Frei collided with Steven Birnbaum in the 29th minute and came down hard on his shoulder, it looked like he had sustained a potentially serious injury. That Frei remained in seemed to be a good sign, though.

Not so much, it turns out.

Although Frei was able to play about 15 more minutes, he eventually came out just before halftime holding his left arm. After halftime, he was wearing a sling. The injury wasn't season-threatening, but it's still not clear how long Frei will be out with a left shoulder sprain

"It wasn't a dislocation, it wasn't a separation," Sounders head coach Sigi Schmid told the media after the game. "Those are the injuries you're worried about. Without that happening, it's just got to calm down and then it's almost like a pain threshold kind of thing and how quickly your range of motion comes back."

If the injury is deemed just a "Grade I" sprain, it's possible that Frei could be back in just a week or two.

Up until his removal in this game, Frei had played in every minute of every Sounders regular-season game since signing with them before last season. Despite not getting credit for the shutout in this game, Frei leads MLS with eight and is the league-leader in saves. He's also second in wins and save percentage.