Erling Haaland scored with his first touch for Dortmund, before completing a hat-trick, with the Norwegian striker stepping off the bench against Augsburg to show Manchester United what they are missing.
Having become the most sought-after striker in European football, the 19-year-old snubbed United to move to Dortmund.
However, Haaland made an immediate impact after being handed his debut off the bench just before the hour mark against Augsburg.
The youngster, who had been prolific for his previous team Red Bull Salzburg, also required just one touch to score his first goal for the club.
His introduction helped Dortmund, who were facing up to a frustrating afternoon, to turn a thrilling game with Augsburg on its head.
The forward grabbed them a lifeline, before Jadon Sancho restored parity shortly afterwards for Dortmund.
Having been signed to make an impact for the German side in the final third, Haaland collected a first match ball in Germany in the 79th minute.
With Augsburg reeling, the youngster completed his hat-trick in 23 minutes of joining the action – joining Pierre-Emerick Aubameyang as the only man to score a treble on debut for the team.
Dortmund will be hoping that this is just the start for their new striker, with United left to reflect on what could have been as they turn to alternative targets in the winter window.
