Kylian Mbappe claimed Paris St Germain "played like beginners" after they suffered their heaviest Ligue 1 loss in 18 years on Sunday.
Needing to avoid defeat to seal the title, PSG instead suffering a humbling 5-1 reverse to second-placed Lille, collapsing in the second half after the dismissal of Juan Bernat.
Bernat had cancelled out Thomas Meunier's own goal in a first half that saw Mbappe twice denied for offside, but once down to 10 men, PSG conceded efforts to Nicolas Pepe, Jonathan Bamba, Gabriel and Jose Fonte.
"It was an end-to-end match," Mbappe told Canal Plus.
"One moment we were on top, the next we were not. We can afford to lose, we will still be champions, but we cannot lose like this, not with three, four or five goals conceded.
"We must play with more personality. This is a problem we must correct.
"Football is played on the pitch. It is not about just saying things. We played like beginners and we must not lose like that."
Coach Thomas Tuchel disagreed with his striker, and pointed to a long list of absentees which grew with Thiago Silva and Meunier hobbling off in the first half.
"We did not play like beginners – it is too easy to say that," he said in his post-match press conference. "We scored three goals against Lille but two were offside.
"There were no chances for Lille in the first half, and we had an opportunity to score a second goal.
"Moussa Diaby has played only twice and (Thilo) Kehrer is sick – ordinarily they should not be with us, but here we are.
"Bernat played on the left, then the middle, it's not normal. It shows the extraordinary mentality we have had, but it's too much.
"Marquinhos is sick, Thiago Silva is injured. Lille are a fantastic team and with 10 men it was complicated but we played well."
Tuchel admitted he may struggle to put out a side against Nantes with Marco Verratti picking up a booking to earn a suspension, adding to that facing Bernat.
While PSG lick their wounds, Lille are getting used to the idea of Champions League football after moving eight points clear of Lyon in second place.
"There are 18 points left to play for – so I will let my players enjoy this for 48 hours, even if they have training on Monday," said a delighted Christophe Galtier.
"We are in a good second place in terms of average points, taking two points per game. It's a good performance."
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