Paris Saint-Germain blew a third chance to claim the Ligue 1 title as they slumped to a morale-sapping 3-2 loss at Nantes on Wednesday.
Thomas Tuchel watched from the stands as a patchwork side ravaged by injury failed to protect Dani Alves' stunning opener and fell to a second straight defeat, having been thrashed 5-1 at second-placed Lille at the weekend.
There was perhaps more embarrassment in conceding three times to a relegation-threatened team they had beaten in each of their past 14 top-flight meetings.
Diego Carlos did the bulk of the damage for Nantes with two goals either side of Majeed Waris' tap-in in the 44th minute.
And, though substitute Metehan Guclu grabbed a late consolation for PSG, their eventual celebrations of a sixth title in seven seasons look certain to be muted.
PSG needed a lift after their crushing loss to Lille and appeared to have it when wing-back Alves lashed a sweet 30-yard strike over Maxime Dupe in the 19th minute.
That joy disappeared barely three minutes later as Diego Carlos nodded in Valentin Rongier's corner, and Nantes compounded the away side's misery shortly before the break.
Kalifa Coulibaly dispossessed Thilo Kehrer and squared for Samuel Moutoussamy, whose side-footed effort was turned in by striker Waris.
The second half brought little defensive improvement for PSG as another Nantes corner evaded several players at the near post and squirmed in off Diego Carlos' standing foot.
A fourth should have followed after Gianluigi Buffon wandered well outside his area but Coulibaly, gifted the ball by Leandro Paredes, shot over an open goal.
Guclu pulled one back via Colin Dagba's cut-back, but the match will be remembered for PSG stumbling into another hurdle in their awkward attempt to cross the finish line.