The hosts, who had home advantage because of their better record over the course of the MLS season, nearly took the lead after two minutes.
The Italian combined with Altidore once again minutes later as he dragged a pass towards the penalty spot, but the Seattle defence cleared the ball to safety.
Neither side managed to break the deadlock in 120 minutes of football, although Toronto created several chances, while Sounders failed to register a single a shot on target.
A late Frei save from Altidore's looping header allowed the Sounders to get penalties and, after Michael Bradley and Alvaro Fernandez each missed in the first five kicks, it was left to Roman Torres to score the winning shot. body check tags ::