Joaquin Torres' late goal proved to be the winner as the Philadelphia Union beat the nine-man Chicago Fire 1-0 at Subaru Park.
Chicago played with ten men from the 50th minute, as Fabian Herbers was shown a second yellow card for a late and high challenge on Kai Wagner.
The visitors thought they were going to hold out for a hard-fought point, but Torres came up with the match-winner as the game headed for stoppage time. His left-footed strike from 20 yards out caught Chicago goalkeeper Chris Brady off guard, as it bounced just in front of the goalkeeper, who could not keep the shot out as it hit the back of the net.
During stoppage time, with the Fire in search of an equaliser, they were reduced to nine men, as Kei Kamara was shown a second yellow card for a high boot on Julian Carranza.
Jim Curtin made wholesale changes to the team that started and drew 0-0 against Alianza in El Salvador in midweek. Club captain Ale Bedoya returned to the starting XI, as did Mikael Uhre and Julian Carranza.
Former Philadelphia forward Kacper Prybylko started up front for Chicago, with Xherdan Shaqiri and Kei Kamara playing with the striker in the attack.
The visitors almost got off to a dream start in the first minute of the game. Shaqiri's free-kick into the box took a fortunate deflection in the direction of Rafael Czichos, who managed to get a shot away. It seemed as if it could sneak into the bottom corner, but it went just wide of the goal.
Carranza was denied by a goal-line clearance in the 14th minute. Kai Wagner's corner from the left dropped to the forward, who did well to keep his volley low and on target. It beat Chris Brady in the Chicago Fire goal but not Gaston Gimenez, who was on the line to clear it away.
Kamara had the ball in the back of the net for the visitors, but it was ruled out for offside. The ball fell to the forward just inside the penalty area, where he thumped it beyond Andre Blake in the Philadelphia goal. However, he was stood just in front of the last man, meaning he was in an offside position.
Bedoya came close in the 24th minute. He did well to bring the ball down after a free-kick into the penalty area was headed as far as him. The midfielder cut the ball back onto his left foot to buy him the time and space to direct a shot goalward. He tried to bend his effort towards the far bottom corner, but it went just wide of the post.
On the half-hour mark, Przybylko came close to scoring against his former team. He did well to get on the end of a cross into the box and directed a header towards the bottom corner. Blake got down to it and pushed it away from danger before the Union cleared their lines.
From the resulting save, the Union were forced into a first change as Blake appeared aggravated by a groin problem. He was replaced by Joe Bendik in the 33rd minute.
HALF-TIME: Philadelphia Union 0-0 Chicago Fire
In the 50th minute, Fabian Herbers was shown a red card for a second bookable offence. The Chicago man caught Wagner with a late challenge which was also high on the defender's leg. It left the referee with no choice but to brandish a second yellow card. Herbers was initially yellow-carded in the first half following a clash with Jose Martinez.
In the 61st minute, Philadelphia made a double substitution, which saw Jack McGlynn and Joaquin Torres replace Leon Flach and Uhre.
The Union had a golden opportunity to go in front in the 76th minute. Torres played a great ball towards the back post, which Daniel Gazdag got on the end of. Instead of trying to head it goalward, Gazdag attempted to cushion his header towards Bedoya, who would have had an open goal at his mercy. However, the ball did not reach the Philadelphia captain as excellent defending from the visitors saw the ball cleared away for a corner, which came to nothing.
Torres remained involved with the play as he tried to flick Olivier Mbaizo's ball into the box goalward. However, he could not test Brady, as his flick-on went wide of the far post.
Gazdag forced Brady into a save in the 87th minute. Carranza set the ball back for the midfielder to curl an effort towards the goal from 20 yards. It appeared that it could be going wide, but Brady palmed it behind for a corner just to make sure of it.
During the final moments of regulation, Torres gave the Union the lead. The forward was allowed to cut inside on his left foot and made his way towards a central position before shooting from over 20 yards out. Torres' effort went through a crowd of players before bouncing in front of Brady and going into the back of the net, as the Chicago goalkeeper could not keep it out.
Moments later, Quinn Sullivan thought he had made it two. The forward found himself through on goal as the Union broke forward. He did well to avoid the challenge of a defender before getting into the penalty area and drilling a low-driven shot across the goal and into the bottom corner. Unfortunately, the youngster's fine work did not count, as the linesman's flag was raised for offside.
Kamara was then shown a second yellow card for a high boot on Carranza as the visitors went in search of an equaliser. It then caused a ruckus as both sets of players clashed, and among that, Kamara was shown a second yellow and his marching orders.
FULL-TIME: Philadelphia Union 1-0 Chicago Fire
Philadelphia Union: Blake (Bendik 33'), Mbaizo (Sullivan 83'), Glesnes, Elliott, Wagner, Martinez, Bedoya, Flach (McGlynn 61'), Gazdag, Uhre (Torres 61'), Carranza
Unused Substitutes: Harriel, Lowe, Real, Bueno, Perea
Chicago Fire: Brady, Souquet (Dean 55'), Teran, Czichos, Navarro, Gimenez (Pineda 65'), Burks, Herbers, Shaqiri (Casas Jr. 76'), Kamara, Przybylko (Mueller 55')
Unused Substitutes: Richey, Haile-Selassie, Omsberg, Gutierrez, Rodriguez