Paris Saint-Germain manager Laurent Blanc insists that his side must take "collective" responsibility for their first Ligue 1 defeat of the season to 13th placed Guingamp.
After losing 3-1 to Barcelona in midweek and finishing second in their Champions League group, PSG lost their unbeaten record as Jeremy Pied's early goal condemned them to defeat.
Even worse, the capital club could not capitalise on Marseille's 1-0 loss to AS Monaco and remain one point behind their title rivals.
"This is not just a bad week, it's a dreadful one," said PSG coach Laurent Blanc. "If we lose because the other side were good that's one thing, but this we cannot tolerate.
"The reality is that this afternoon there was a lack of collective and individual concentration.
"This is our problem. In a team there are leaders, and when it's not going the way you want, these leaders and also the coach, of course, they have to raise their game to ensure that the collective do too.
"Here we must say that tonight we are all put in the same bag, including me, because we have not been able to respond, although in the second half we could have equalised."
With Thiago Silva and David Luiz nowhere to be seen for Pied's goal, PSG midfielder Blaise Matuidi took personal responsibility telling AFP: "It was poor marking all round, even me I got it wrong. We're really upset. We're just not used to losing and now that's two in a week."
Meanwhile goalkeeper Salvatore Sirigu insists they should learn from the defeat.
"We did not play well tonight, obviously," he told the club's official website. "We'll have to work it out with the coach in the week to try to understand what went wrong. We must face the difficulties when the situation is more difficult. When defeat comes, you have to face it without fear."