The Brazilian came off the bench and launched the Fire into Eastern Conference playoff positioning.
With a 3-2 win over New England, Chicago passed the Revolution and drew even with Philadelphia for the fifth and final postseason slot in the Eastern Conference. Juan Luis Anangono and Mike Magee also struck for Chicago, while Kelyn Rowe and Saer Sene scored for New England.
New England jumped ahead in the ninth minute. Collecting a layoff from Sene, Rowe picked his head up 25 yards from goal and struck a looping shot over goalkeeper Sean Johnson and in.
Against the run of play, Chicago equalized in the 30th. Connecting with a needle-threading pass from Joel Lindpere, Anangono took one touch in traffic to settle the ball and used his second to slot a shot past Bobby Shuttleworth.
But the Revolution would regain the lead moments before halftime. Found lurking on the left side of the box by Dimitry Imbongo, Sene fired home a low one-time shot.
The Fire would again draw level in the 55th minute. Patrick Nyarko hit a slow-rolling pass toward goal, and as Anangono shielded off a defender, Magee ran onto the ball and tucked his left-footed shot in.
Alex notched the winner in the 86th minute. As a Fire corner was cleared, Alex collected the ball at the top of the box and launched a shot that just snuck betwen Shuttleworth and the post.