Paris Saint Germain's stuttering form continued after going down 3-2 to Montpellier in a Ligue 1 clash on Tuesday evening.
Following their cup final heartbreak, PSG re-instilled Gianluigi Buffon, Leonardo Paredes and Eric Choupo-Moting against a side chasing European football next season.
Montpellier, who were hammered 5-1 in the reverse fixture this season, were behind on 12 minutes, as Ambroise Oyongo shipped Junior Bernat's cut back into his own net.
The French champions surrendered control on 21 minutes after Pascal Kimpembe tucked Damien Le Tallec's wayward header past Buffon.
Kimpembe's struggles continued on 31 minutes, allowing Delort a shot which Buffon tipped away, before getting down to push Ellyes Skhiri's effort wide.
Barely three minutes to halftime, Delort was send through again and flunged Gaetan Laborde's assist over the top from point-blank range.
Straight from resumption, PSG installed a change in Layvin Kurzawa for Cameroonian international Choupo-Moting.
Montpellier continued pushing and on 58 minutes, Buffon staved off Florent Mollet's long-range half-volley.
The Parisans were back in front on 62 minutes after Angel Di Maria tweaked past Benjamin Lecomte for an easy finish.
Montpellier made their first change after 73 minutes, as midfielder Paul Lasne came on for Mathias Suarez.
From a few guilt-edge misses, Delort made up for lost time in the last 10 minutes with a composed finish from Mollet's pass.
Montpellier brought on Souleymane Camara and Junior Samba, and the latter's corner on 85 minutes met Camara, who saw his header cleared off the line by Paredes.
The third eventually came as poor communication between Paredes and Buffon set up Camara, who applied a stunning first-time finish seconds later.
The defeat is the Parisans second within a week, with pressure sure to grow on embattled manager Thomas Tuchel.