It took until late in the second half for Sporting KC to finally break through the defensive wall that St. Louis FC set up for most of the game, but Graham Zusi finally punched through with a goal to send Sporting KC to the fifth round of the US Open Cup.
This extended Sporting KC's unbeaten run in all competitions to eight matches.
The first big chance for Sporting KC came in the 17th minute when Dom Dwyer found himself on the end of a Graham Zusi set piece. He directed a powerful header towards goal but his bad luck continued this season as it clanged off the crossbar and was cleared away to end the threat.
St. Louis FC came close to taking advantage of a defensive mistake by Sporting KC in the 32nd minute. Amadou Dia made an errant pass that was intercepted by Jeremy Lynch and passed ahead to Mike Ambersely but it was out of his reach as Tim Melia came sprinting out 40 yards away from goal to meet the ball and clear it before St. Louis could get a chance to shoot.
On the defensive end, St. Louis FC continued to pack it in, leaving Sporting KC with few decent opportunities inside the box and the home side's reluctance to take a shot from distance meant that St. Louis FC keeper Mark Pais was hardly troubled in the first half. The team's best save actually came in the stoppage time of the first half with a goal-line clearance from Mike Ambersely.
Graham Zusi took the ball in the box after a slow cross from the wing and flicked it towards goal, seemingly out of the reach of Pais. Ambersely, however, was in the right place at the right time and cleared the ball away to keep the match scoreless as the two sides went into the locker room at the break.
Zusi continued to be an attacking threat in the second half and brought the ball into the box in the 55th minute, where he juked past two defenders but was tripped up moving towards the center of the box. There was no whistle, however, and the match continued with no penalty.
It wasn't until the 70th minute that Sporting KC got their breakthrough. After threatening in the St. Louis half for the better part of five minutes, Benny Feilhaber sent in a quality ball in the air that Graham Zusi redirected with a header to put Sporting KC in the net and on the board. Zusi's goal gave Sporting KC the 1-0 lead with less than 20 minutes to play.
Sporting KC almost added to their lead in the 75th minute when Dom Dwyer got behind the defense and only had one defender contesting his shot, but he blazed it way over the bar to end the threat.
Although the home side were controlling the tempo, St. Louis did have a couple of late chances. In the 82nd minute, Ambersely lead the charge on a counter attack that he took into the box himself and attempted a near post shot that was rocketed over the bar to keep St. Louis scoreless.
Sporting KC, however, held on for the final ten minutes to take the fourth round victory over their I-70 rivals 1-0. They advance to the fifth round of the tournament as part of the final sixteen teams left. They will learn their opponent Thursday in a live-streamed draw at 10 a.m.