Borussia Dortmund head coach Lucien Favre bemoaned his side's impatience after they suffered a shock 3-1 defeat at Bundesliga newcomers Union Berlin.

On-loan winger Marius Bulter struck in both halves, either side of Paco Alcacer's equaliser, before Sebastian Andersson sealed Union's first ever victory in the German top flight.

The loss was Dortmund's first of the season, having started their campaign by coming from behind to beat both Augsburg and Cologne, as Union were left toasting a memorable day in their 53-year history.

Favre told Dortmund's official website: "It was the difficult game we were expecting. Our first half was good. We had two good opportunities and quickly equalised at 1-1.

"I think in the back of our minds we were thinking it'd be like the second half in Cologne. That wasn't the case.

"Union continued to play a very committed game, showed a strong physical presence and countered very well upon regaining the ball.

"We should've remained patient and not allowed ourselves to be hasty with the score at 1-1; rather, we needed to defend very well. That's very important.

"Instead, we became impatient and then conceded an unnecessary goal to go 2-1 down. Then, too, we should've remained patient. There was still time to make it 2-2 and perhaps even to win the match.

"Our second half wasn't good."

Dortmund captain Marco Reus was even more critical of their performance, saying: "We were simply completely stupid the whole game.

"Every one of us has to up their game and we'll have to start in two weeks' time (after the international break)."