Paris Saint-Germain's defensive liabilities were exposed again as it slumped to a 4-2 defeat at Bastia and slipped to fourth in the French league, after leading 2-0 inside 20 minutes on Saturday.

PSG has failed to win any of its past three league games, losing two and drawing one.

Coach Laurent Blanc's side squandered the chance to close the gap on league leader Marseille, which lost 2-1 at Montpellier on Friday, and remained three points behind. This latest sloppy performance increases the pressure on Blanc ahead of Tuesday's League Cup quarterfinal at Saint-Etienne.

"Yes, we were complacent at times. The three points were within our reach," Blanc said. "You get taught a good lesson when you don't do things properly."

To make matters worse, Saint-Etienne's 2-1 win at Reims saw it leapfrog over PSG and into third place. Saint-Etienne is level on points with Lyon, which has a better goal difference and can move to the top of the league if it beats Toulouse at home on Sunday.

Saint-Etienne's goals came either side of halftime from wingers Yohan Mollo and Romain Hamouma.

Before the winter break, Blanc lamented his team's lack of aggression and rigor, particularly when defending set-pieces - and two of the goals conceded came from corners and two stemmed from crosses.

"It's a big mistake from us; we woke Bastia and their fans up. We have no right to do that," Blanc said, adding that "conceding four goals is inexplicable."

A minute's silence was held before all matches this weekend in memory of the 17 people killed in Paris this week, following three days of bloodshed in a rampage by terrorists linked to al-Qaida in Yemen.

The game started brightly for PSG.

Winger Lucas scored in the 10th minute after running onto Yohan Cabaye's precise pass, and midfielder Adrien Rabiot capped a rare start with the second 10 minutes later, after being set up by Javier Pastore.

Bastia scored in the 32nd after right back Gregory van der Wiel was ruled to have handled the ball following a cross, and midfielder Ryad Boudebouz confidently converted the penalty.

That goal boosted the Corsican side's confidence - and Boudebouz's.

The midfielder set up the equalizer on the stroke of halftime when his cross was headed home by veteran defender Francois-Joseph Modesto - despite the close attentions of defenders Maxwell and David Luiz.

PSG striker Zlatan Ibrahimovic, who has scored only once in his past four games, was kept largely quiet and Bastia took the lead soon after the break when defender Julian Palmieri struck the best of his two goals.

After Rabiot cleared Boudebouz's corner from the left, the ball fell to Palmieri some 20 meters out, and he hit a splendid volley to make it 3-2 in the 56th.

PSG went close to equalizing as center half Thiago Silva struck the crossbar and Lucas flashed a header just wide, but Palmieri sealed an impressive win when he rifled in Abdoulaye Keita's cross from the right.

In other matches, it was Evian 1, Rennes 1; Guingamp 2, Lens 0; Lille 1, Caen 0; and Nice 3, Lorient 1.

Also on Sunday, Nantes hosts Metz and Monaco faces Bordeaux.