Having conceded five times inside the opening 25 minutes across their previous three outings, Dortmund again looked shaky to begin with, and efforts from former Dortmund full-back Tom Rothe and Benedict Hollerbach were mere warnings for another within that period.
They were unheeded, and Nico Schlotterbeck dangled out a leg to send Hollerbach tumbling for a penalty. There was a surprise in store though, as Kevin Vogt stepped up to take it.
The central defender coolly dispatched from 12 yards, giving no clues as to why that was incredibly his first Bundesliga goal in 275 matches – an all-time league record for an outfield player.
Remarkably, three of Vogt’s four career Bundesliga goals had now come against Dortmund, and his strike inspired them to continue in the same vein.
They couldn’t turn in a dangerous ball across the face from Hollerbach initially, but they deservedly doubled their lead on the stroke of half-time through Yorbe Vertessen, who gathered up a cleared corner on the edge of the box and unleashed a powerful low strike through a crowd of bodies and beyond Gregor Kobel.
With no choice other than to try and replicate their comeback to win 4-2 from this position against Bochum last weekend, Dortmund finally began to forge opportunities of their own.
The best of those was a fast counter which found Maximilian Beier bearing down on goal in acres of space, but Frederik Ronnow was equal to it with a reaction save.
Despite that miss, the deficit was still halved just a few minutes later as Julian Brandt released Julian Ryerson, who executed a composed right-foot finish to pull one back against his former employers.
The pressure on the Union back line was immense as the away side chased an equaliser, but shots from Vertessen, Hollerbach and Tim Skarke showed that they could be a real threat on the counter themselves.
Die Eisernen stood strong though, and recorded a fourth win in seven competitive matches under Bo Svensson, duly leapfrogging Nuri Sahin’s side into a provisional top-six placing.
Flashscore Man of the Match: Yorbe Vertessen (Union Berlin)
