The in-form South Korean’s 18th-minute strike settled a tempestuous encounter that saw both sides reduced to ten men after Emir Spahic and Sokratis picked up red cards late on.
Son on target
Boosted by three consecutive wins in all competitions, Dortmund began confidently, carving out the first promising chance after only three minutes when Pierre-Emerick Aubameyang passed across the face of the goal and Robert Lewandowski saw his effort denied by goalkeeper Bernd Leno. It soon became clear, however, that Leverkusen had come to the Signal Iduna Park in high spirits after booking their place in the last eight of the DFB Cup against SC Freiburg in midweek, with the deep-lying visitors looking to hit the opposition on the counter at any given opportunity.
Sami Hyypiä's men issued their first serious warning ten minutes into the game when Son did well in shaking off two defenders before cutting it back to Jens Hegeler, whose right-footed long-range effort was well met by BVB custodian Roman Weidenfeller. Emre Can forced the Germany international into action with another testing effort, before Son went one better, rounding Weidenfeller to send the ball home for his sixth goal in his last four Bundesliga outings.
Dortmund reacted well to that setback and began to enjoy the lion’s share of possession, though clear-cut goalscoring opportunities proved hard to come by as Leverkusen's well-marshalled defence reduced the five-time champions to a number of long-range attempts, with Lewandowski and Nuri Sahin going closest. Bayer 04 remained extremely dangerous on the break, meanwhile, with Son spurning a one-on-one with Weidenfeller and Hegeler's chip nearly helping the guests to a two-goal half-time lead.
Having to deal with a half-time deficit for the first time this term and looking to avoid back-to-back home defeats for the first time in over four years following the Matchday 13 loss to Bundesliga leaders FC Bayern München, Dortmund emerged after the break with purpose, but came up against a Leverkusen defence in no mood to surrender their lead.
With die Schwarz-Gelben lacking the necessary creativity in the final third of the pitch, head coach Jürgen Klopp tried to add fresh impetus to the BVB attack a good hour into the game by introducing Marco Reus, back from a calf injury, and Jonas Hofmann, with the hosts' hopes of staging a late comeback given further cause for optimism when Bayer centre-back Spahic received his marching orders ten minutes from time.
Lewandowski almost got the breakthrough for Dortmund, who themselves had to see out the remainder with ten men following Sokratis' second-bookable offence. Both Aubameyang and Reus were presented with further promising opportunities, but it wasn't to be for Borussia, who now trail Leverkusen by six points and Bayern by ten.
Line-ups and statistics