Peter Bosz lamented Borussia Dortmund's inability to make a numerical advantage count after his side were held to a 0-0 draw by 10-man Freiburg on Saturday.
Freiburg debutant Yoric Ravet was dismissed after a Video Assistant Referee review just before the half-hour mark for a reckless challenge on Marcel Schmelzer, referee Benjamin Cortus having initially brandished a yellow card.
"I'm disappointed," Bosz told reporters. "When you play for an hour with a man extra, you must win. There is enough time to score.
"To leave with a draw isn't enough. That was not enough today. For us, there are two lost points."
Schmelzer had to be withdrawn as a result of Ravet's tackle and midfielder Gonzalo Castro blamed referee Cortus for setting the tone by failing to strictly punish earlier challenges.
"This is the problem: if you, as a referee, do not give an early sign with a yellow card then something happens, like this foul, and one of us is hurt again," he said.
