Brendan Rodgers acknowledged Celtic were beaten by the better side in their Champions League clash with Borussia Monchengladbach, adding that the Scottish champions are still learning at the highest level.
Second-half strikes from the excellent Lars Stindl and the equally impressive Andre Hahn secured a convincing 2-0 win for Andre Schubert's side at Celtic Park on Wednesday.
The defeat leaves Celtic bottom of Group C with just one point to their name and former Liverpool boss Rodgers conceded his men were struggling with a steep learning curve.
"They were better than us, that's the sum of it," Rodgers told BT Sport.
"Our players gave everything, but they were a bit sharper and quicker than us. We know that that's the level we have to aspire to in the next few years.
"It was always going to be difficult for the team, but for us we're learning in every single game at this level. We were just beaten by a better team."
Both of Gladbach's goals came directly from mistakes by Celtic's veteran defender Kolo Toure, who has followed Rodgers from Anfield to Glasgow.
However, Rodgers was quick to shake off the assertion that the Ivorian's faults were the reason for the defeat.
"In games like that you don't want to gift anything - we probably gifted the two goals," Rodgers added.
"[Kolo] is a top professional. He has been outstanding since he came here.
"When you ask players to play from the back people make mistakes - but it happens and there's no blame attached."
For his part, though, ex-Arsenal and Manchester City defender Toure was slightly more damning of his performance.
"In this type of competition we can't afford to make those mistakes and I have to blame myself because it was a simple action to put the ball away both times," he told BT Sport.
"But I like to make sure the team have the ball, maybe I was overconfident.
"I don't like to make mistakes, but they happen. Even though I'm 35, I'm still making mistakes like a 16-year-old."