Borussia Dortmund captain Emre Can said his side failed to "push past the pain barrier" in Tuesday's 1-1 home draw with Lille in their Champions League last-16 first leg.
A 22nd-minute Karim Adeyemi goal was the highlight of a first half where last season's Champions League finalists Dortmund dominated proceedings.
In the second half, the German club allowed Lille back into the game, with Jonathan David setting up Hakon Haraldsson for a 68th-minute equaliser, leaving everything to play for next week in France.
After a disappointing season in all competitions, having fallen to 10th in the Bundesliga and exiting the German Cup in the second round, Dortmund looked to have turned the corner after new coach Niko Kovac's January arrival.
Dortmund had kept four clean sheets in six matches under Kovac and came into Tuesday's game having won two straight league fixtures for the first time this season.
But a flaccid showing at home against a team sitting fifth in Ligue 1 shows Kovac has plenty of work to do to rebuild the flagging side.
"The second half was not good at all. Too little intensity off the ball and too little ball possession," Can told Amazon Prime.
"We didn't push past the pain barrier – and that's what you need to do against Lille. They're a good team – they're here in the last 16 for a reason.
"We need to be more courageous – it wasn't good enough today. We can do better and we will."
Despite the disappointment, Can said Dortmund would "travel there (Lille) riding high – we believe we can stay in the competition".
Midfielder Pascal Gross, who had a goal ruled out for offside, said Dortmund "lacked intensity".
"We lost the ball too often – it was simply not good," said the former Brighton player.
"(But) we're starting at 0-0 next week. It'll be tough but we've also got our strengths. We want to win there and keep going."