Against a better side, PSG would likely have lost and the poor defending was hardly encouraging heading into a Champions League last-16 showdown against free-scoring German side Borussia Dortmund later this month.
Winger Ángel Di María, striker Kylian Mbappé and club top scorer Edinson Cavani all scored for PSG, while Lyon center back Marcal netted an own-goal. Forwards Martin Terrier and Moussa Dembélé rallied for Lyon early in the second half.
In windy conditions at Parc des Princes, because of Storm Ciara hitting northern Europe, Lyon had the first chance when Terrier shot just wide. Moments after Dembélé failed to make the most of a chance, PSG counterattacked and Di María gathered the ball on the right, jinked to the left and drilled a low shot inside the near post.
For all of Lyon's ability in attack, the midfield is soft and the defense fragile. PSG's second goal came from another routine long pass which Lyon failed to deal with. The ball went quickly from striker Mauro Icardi in midfield to Thomas Meunier charging down the right. The Belgium right back's deflected cross from the right rolled to Mbappé near the penalty spot, and he clipped it adroitly over goalkeeper Anthony Lopes.
Two minutes after the break, Marcal's own-goal happened when he turned in Julian Draxler's cross. Terrier pulled the first goal back in the 52nd, slotting the ball under goalkeeper Keylor Navas after being set up by 16-year-old midfielder Rayan Cherki — who is being touted as a star of the future.
PSG's defense panicked on Tuesday after conceding midway through the second half in a 2-1 win at Nantes, and the same happened again. Dembélé made it 3-2 seven minutes later after being set up by substitute Karl Toko-Ekambi, but then missed a great chance when he curled a shot just wide as he slid to meet a pass from the right.
Mbappé hit the crossbar before substitute Cavani gave PSG some breathing space with his 199th goal for PSG after being set up by Di María's unselfish cut-back in the 79th. Lyon's eighth defeat of the league campaign leaves it in ninth spot and drifting away from the European places for next season.
OTHER MATCHES Andy Delort's first-half goal helped 10-man Montpellier beat struggling Saint-Etienne 1-0 and move up to fifth place. Delort met Junior Sambia's first-time cross, whipped in from the right, with a thumping header which flew past goalkeeper Stéphane Ruffier in the 25th minute.
But after Sambia's sending off in the 42nd, Montpellier was on the back foot. Saint-Etienne's 12th defeat of the season leaves it sliding toward the relegation zone in 15th place. Strasbourg climbed to sixth, one point behind Montpellier, after beating midtable Reims 3-0 at home.
All the goals came in the second half, through center half Alexander Djiku, forward Majeed Waris and right back Kenny Lala's last-minute penalty.
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