PARIS, France (AFP) — Holders Liverpool began their defence of the Champions League trophy with a defeat against Napoli yesterday, while one missed spot-kick condemned Chelsea to defeat against Valencia and another came to Barcelona’s rescue.

Liverpool survived a 0-1 defeat in Naples in the group stage last season to go on and win their sixth European Cup; and this time a 0-2 loss at the San Paolo made them the first reigning champions to lose their opening game in the competition since AC Milan in 1994.

Both sides had chances in the Group E clash before the hosts won a late penalty with barely 10 minutes remaining when Jose Callejon went down under an Andy Robertson challenge.

Dries Mertens beat Adrian from 12 yards and substitute Fernando Llorente — who played for Tottenham Hotspur against Liverpool in last season’s final — then took advantage of a rare defensive lapse by Virgil van Dijk to make it 2-0 in stoppage time.

Liverpool must now bounce back in two weeks when they host Austrian champions Salzburg, who made a stunning return to the group stage as teenage forward Erling Braut Haaland netted a hat-trick in a 6-2 demolition of Genk.

Salzburg had fallen in the qualifying rounds in the last seven campaigns but finally progressed this season to the group stage for the first time since 1994-95.

Haaland, the teenage English-born Norwegian striker whose father, Alf-Inge played for Manchester City, gave Salzburg a second-minute lead and netted twice more before half-time.

Aged just 19 years and 58 days, Haaland is the third-youngest player to score a Champions League hat-trick behind Wayne Rooney and Raul, according to sports statisticians Opta.

The South Korean Hwang Hee-Chan and Dominik Szoboszlai also struck before the break for Salzburg, while captain Andreas Ulmer completed the rout in the second half.

Jhon Lucumi and Tanzanian striker Mbwana Samatta scored for the Belgian champions.

Last season’s Europa League winners Chelsea ensured it was two defeats out of two on the night for English sides as they lost 0-1 at home to Valencia.

The Spaniards scored in the 74th minute when a Dani Parejo free kick was converted by Rodrigo Moreno. Chelsea were given a chance to rescue a draw when Daniel Wass was penalised for handball in the box, but Ross Barkley’s 87th-minute penalty hit the bar and went over.

Also in Group H, last season’s semi-finalists Ajax claimed an impressive 3-0 home win over Lille, with two of their newest signings among the goals.

Quincy Promes headed the Dutch champions in front and the Mexican Edson Alvarez doubled their lead early in the second half before Nicolas Tagliafico sealed the win.

,After a patchy start to the season, Barcelona will be relieved to escape from their trip to Borussia Dortmund with a 0-0 draw, as Lionel Messi returned from injury as a second-half substitute.

The home side will feel they should have won, but Marco Reus had a second-half penalty saved before Julian Brandt hit the bar late on.