Chelsea have opened an internal investigation after their team lineup was allegedly leaked before their crushing 5-2 Champions League defeat to Paris Saint-Germain.

Head coach Liam Rosenior confirmed the probe following the damaging first-leg loss in the round of 16 at the Parc des Princes.

PSG took the lead through Bradley Barcola in the 10th minute, but Malo Gusto equalised for Chelsea in the 28th. Ballon d’Or winner Ousmane Dembele restored PSG’s advantage just before halftime.

Chelsea briefly fought back after the break when Enzo Fernandez equalised in the 57th minute. However, a costly error from goalkeeper Filip Jorgensen allowed Vitinha to make it 3-2 before Khvicha Kvaratskhelia sealed the victory with two late goals.

Speaking after the match, Rosenior admitted he had not been aware of the reported lineup leak but insisted the club would investigate the matter.

“I wasn’t aware. I’m sure we’ll get to the bottom of that if that’s the case,” he told The Chelsea Chronicles.

Chelsea now shift focus to the Premier League, where they host Newcastle United on Saturday before attempting to salvage their Champions League hopes in the second leg next Tuesday.