Paris Saint-Germain slumped to a dismal 2-0 defeat against Rennes in Ligue 1, with Karl Toko Ekambi and Arnaud Kalimuendo netting to amplify the pressure on Christophe Galtier.
PSG were booed off at half-time by the Parc des Princes crowd after Toko Ekambi broke in behind to hand Rennes a surprise lead, following a series of misses from Kylian Mbappe.
Things quickly went from bad to worse for the disjointed leaders, with former PSG forward Kalimuendo converting Lesley Ugochukwu's cross to provoke more fury from the home fans.
PSG's four-game winning run in Ligue 1 ended with a whimper as Rennes stood firm, and Galtier's under-fire side could see their lead at the summit reduced to seven points when Marseille visit Reims later on Sunday.
Mbappe endured a bad first half for PSG, seeing a one-on-one finish disallowed for offside 22 minutes in before squandering three good opportunities.
Having drilled one left-footed effort narrowly wide, Mbappe was twice released in behind by measured throughballs from Lionel Messi, only for Steve Mandanda to deny him with firm saves.
Mbappe's misses were punished on the stroke of half-time as Rennes scored against the run of play – Toko Ekambi latching onto a simple ball over the top to fire into the bottom-left corner.
PSG found themselves 2-0 down within three minutes of the restart, Kalimuendo side-footing home after Marco Verratti's giveaway allowed Ugochukwu to break down the left.
Toko Ekambi and Kalimuendo almost claimed braces as Rennes continued to press – the latter denied by a one-on-one save from Gianluigi Donnarumma.
Verratti forced a flying save from Mandanda late on, but that was as close as PSG went.