Michael Ambrose and Trevin Cesar scored for Austin in the victory, which will play on the road against the Houston Dynamo of MLS in the Fourth Round.
The match got off to an even start with both sides looking to assert themselves. This created a tight midfield battle with chances rare in the early stages.
Guaraci Oliviera tried to liven up the match as he found space 25 yards out and shot. The swerve caught out Daryl Sattler who just got enough on it to send it out for a corner.
San Antonio may have had plenty of the ball but they just struggled to do anything with it, with Austin giving away plenty of fouls which broke up the flow for the Scorpions. The best chance for the Scorpions came in the 18th minute as a through ball for Billy Forbes forced Devin Perales off his line, only for Forbes to send his effort just wide.
After a lengthy lull in the match the Scorpions seemed to have control and in the 29th minute they had another opportunity. It came from a free kick as the cross came in to Zourab Tsiskaridze but he sent his header wide of goal.
The best chance on the latter stages came after a poor backpass allowed Eric Hassli a chance but he sent his effort wide of goal. San Antonio manager, Alen Marcina was obviously not happy as he brought on Rafael Castillo and Stephen DeRoux at halftime in an effort to get back into the match.
Those changes did not work as Austin hit the lead early in the second half thanks to back to back corners, which created confusion. The ball spilled out for Ambrose who hit it powerfully back past Sattler to open the scoring.
There was a great opportunity for the Scorpions on the hour mark as the ball was squared for a rushing Castillo. His powerful shot came from the edge of the area, but it was well-saved low by Devin Perales, which allowed Austin to clear.
Castillo was again set up after some neat work from Stephen DeRoux down the left. His square ball caught out the Austin defense, allowing him to shoot powerfully but Perales got down well and made the save.
After the Scorpions had a shout for a penalty denied in the 76th minute, Austin found their second thanks to a counter. The Aztex worked the ball up to Julio Cuero who sent the ball back for Cesar who made no mistake, sealing the win.
The Scorpions thought they had a goal in the 81st minute as the ball was in the back of the net but the goal was disallowed as two Scorpions players were caught by an offside trap.
With that as the last chance, the Aztex advanced to a smattering of boos from a frustrated San Antonio crowd.
The frustration boiled over afterward as San Antonio’s DeRoux and Julius James were given post-match red cards. Obviously, since the Scorpions are eliminated, those one-game bans will take effect the next time those players participate in the tournament.