It was just a second defeat for Würzburg since their promotion to the 2. Bundesliga, whose impressive start to the season had seen them go into the midweek games in second behind leaders Eintracht Braunschweig.
But despite being the better of the two teams for much of the match, an impressive solo goal from Quaner meant that Union will now take their place in the top three.
Díaz and Kroos miss out
Würzburg have emerged as the season’s surprise package so far, going into the midweek fixtures in the second place after three back-to-back wins, including a 3-0 victory against Franconian rivals SpVgg Greuther Fürth at the weekend.
Júnior Díaz was left out of the squad for Würzburg after picking up a knock in the game against Fürth, with Peter Kurzweg slotting into his left-back berth.
Jens Keller’s Union meanwhile took a little longer to get into gear, with just two points from their first three games, but wins against Karlsruher SC and 1860 Munich have helped to propel them up the table.
They were without captain Felix Kroos due to muscular problems, so Eroll Zejnullahu came into the midfield three, with Steven Skrzybski taking the armband.
Würzburg on top but a goalless first half
The hosts, as befitting their position in the table, enjoyed the better of the first half. Elia Soriano couldn’t connected with a Kurzweg cross, before an overhead kick from Tobias Schröck went out. Nejmeddin Daghfous also had a shot saved by Jakob Busk, followed soon after by Soriano shooting wide.
Zejnullahu had Union’s only shots on goal in the early stages, but the first went over a second was saved by Robert Wulnikowski.
Würzburg also had calls for a penalty when Kurzburg went down in the box under pressure from Christopher Trimmel. However the referee ignored the appeals, instead giving a free-kick for offside.
Then within the space of a couple of minutes, both sides produced their best chances to score. Damir Kreilach header a Union corner onto the bar, whilst at the other end Daghfous’s cross was fired over at close range by Soriano.
Quaner makes Würzburg rue their failure to score
Würzburg continued to dominate in the second half. Rico Benatelli was given time to shoot when Kristian Pedersen failed to get the ball from a challenge, however Busk made the save.
Daghfous remained a menace for the Union defence. His shot from the edge of the box went wide, whilst a cross from the right ran just ahead of Marco Königs in the box. By now everyone was having a crack too, with Benatelli and David Pisot also off target.
As the game wore on, substitute Simon Hedlung curled the ball into the box, giving Wulnikowski something to deal with, but almost immediately after Würzburg went down the other end, with Daghfous’s cross palmed out by Busk.
However Würzburg had failed to make their dominance count, and they would be made to pay. Quaner earned his side the three points with a great solo effort, taking it on himself to run the ball into the box before his shot beat Wulnikowski and went in off the post.
Königs went close with a header just over the bar in stoppage time, but it would prove to be a bitter loss for Würzburg, despite having been on top for most of the game.