Neil Harris bemoaned a "disappointing" performance during Saturday's 3-1 Sky Bet Championship defeat to Barnsley at The Den, but stated his pride at what his side have achieved in the first 11 games of the season.
Tom Bradshaw gave The Tykes the lead in the 40th minute, but Lee Gregory - on his 150th Millwall appearance - equalised for The Lions on the stroke of half-time from the penalty spot.
However, Bradshaw and Mamadou Thiam - also from the penalty spot - secured all three points for Barnsley.
"I think it was a game too far for us," said Harris. "I'm disappointed with the performance. I take responsibility for that, because I picked the team.
"Individually and collectively, however, those players have been in excellent form and deserved to play. But, if we're not at our best in every single fixture in the League this season, we'll get beat - home or away. Today, we weren't at our best as a defensive unit.
"We were too stretched and we gave the ball away too much. Ultimately, if you give good players at this level those opportunities, they're going to take them. Barnsley deserved to win the game because they took their chances."
Despite the defeat, the manager stated that there is "no blame culture" at the club and that he feels "proud" of the first couple of months of the season.
"The right side of the defence are a little disappointed with a couple of the goals, but in my time here and now, we don't have a blame culture as this club - we have a learning culture. There's no blame on anyone specific today, but we were too easy to score against.
"But, over the course of the first 11 games of the campaign, I'm proud of what my players have achieved.