Match ends, Chelsea 0, Valencia 1.
Chelsea's return to the Champions League ended in disappointment as Ross Barkley missed a late penalty that ensured Valencia claimed victory at Stamford Bridge.
Frank Lampard's first game as a manager in the tournament he won as a player with Chelsea in 2012 turned into a night of frustration as Valencia took advantage of slack marking at a free-kick for Rodrigo to score the winner on 74 minutes.
Chelsea, who lost in-form youngster Mason Mount to injury early on, had the chance to rescue a point when referee Cuneyt Cakir awarded a penalty for handball after consulting VAR when Daniel Wass blocked Fikayo Tomori's header.
Barkley had only come on as a substitute eight minutes earlier but insisted taking the spot-kick instead of the Blues' regular taker Jorginho and Willian, who argued his own case to take it before relenting.
It was a tight and tense encounter with chances at a premium and a tricky Group H, which also includes Lille and last year's semi-finalists Ajax, has got even tougher for Chelsea after starting their campaign with a damaging home loss.
Chelsea lack touch of class
This was a tough start to life in the Champions League for Lampard and a Chelsea side robbed of the 'X Factor' given to them for so long by Eden Hazard.
The mood in the camp will not have been helped by Barkley's insistence on taking that ill-fated late penalty when it appeared Jorginho, who scored in the Super Cup final against Liverpool, was stepping forward for the task.
Barkley's determination came at a heavy price, glancing a poor effort off the bar and high into the Matthew Harding Stand. He took the kick after conversations with Jorginho, Willian, Tammy Abraham and captain Cesar Azpilicueta.
It ended with a handshake from Jorginho before the spot-kick but it was a chaotic scene with an almost inevitable conclusion.
It was a night when not much went right for Chelsea, starting with what looked like a nasty ankle injury to Mount, who was caught by a reckless follow-through in a challenge by former Arsenal midfielder Francis Coquelin.
Chelsea had their moments, especially when Jasper Cillessen saved from Willian and Marcos Alonso - but Lampard's side simply could not produce the touch of quality to break down Valencia and were too static as Daniel Parejo's free-kick released Rodrigo.
This means Chelsea are on the back foot only 90 minutes into their return to the Champions League and are still to win at Stamford Bridge this season.
Valencia lift the gloom
Chelsea's disappointment will be even more acute as this looked like the perfect opportunity to get their Champions League campaign off to a winning start against a Valencia side who arrived in London amid turmoil.
Valencia's players and fans had been infuriated by the decision to sack coach Marcelino last week after he won the Copa del Rey last season and took them back into the Champions League.
Marcelino's successor Albert Celades started his reign with a 5-2 defeat at Barcelona on Saturday - but his Valencia side showed plenty of resolve here and were always a threat, which was realised by that free-kick that was just too quick and too smart for Chelsea and resulted in Rodrigo's goal.
This was a real morale booster for Celades and Valencia but a serious blow for Chelsea as Ajax signalled their threat in Group H with a 3-0 win over Lille.
Tough night for Chelsea's young guns
Chelsea's young brigade have taken the Premier League by storm with Tammy Abraham scoring seven goals and Mason Mount on the mark three times.
Abraham found this a much tougher assignment although he still had moments of threat, particularly a glancing first-half header that was off target.
The 21-year-old never lost heart but he was starved of decent service and this was not to be his night.
It was even more painful for Mount, literally, as he never recovered from Coquelin's early challenge and his attempts to carry on ended in despair. He and Chelsea will now anxiously await the medical verdict.
Defender Tomori did well in defence and also made his contribution in attack with a surging first-half run that brought danger and a header that resulted in the penalty.
There will be better nights than this but the Champions League will be adding layers to their learning experience.
Rare losing start for Chelsea - key stats
- This was only Chelsea's second defeat in their past 42 Champions League group games at Stamford Bridge (W30 D10), with the other against Basel in 2013.
- Chelsea lost their opening Champions League match of a campaign for only the second time - the first was against Basel in 2013-14.
- Frank Lampard became the first Chelsea manager to lose his opening Champions League match in charge - 10 of the previous 11 had won, while Gianluca Vialli drew with AC Milan in 1999.
- Chelsea became the first team since Liverpool in December 2008 against PSV (Darby, Kelly, Spearing) to hand three Champions League debuts to Englishmen aged 21 or younger in the same game (Abraham, Mount, Tomori).
- Valencia registered only their second away Champions League win in England (D7 L3) - their first was a 1-0 win at Liverpool in October 2002.
- 15ZoumaSubstituted forGiroudat 73'minutesBooked at 90mins
- 5JorginhoBooked at 33mins
- 17KovacicSubstituted forBarkleyat 80'minutes
- 19MountSubstituted forPedroat 16'minutes
- 17CoquelinBooked at 9mins
- 11CheryshevSubstituted forDiakhabyat 90+2'minutes
- 19RodrigoSubstituted forLeeat 90'minutes
- 9GameiroSubstituted forGómezat 70'minutes
- 7Gonçalo Guedes
- Cüneyt Çakir
- Shots on Target
Second Half ends, Chelsea 0, Valencia 1.
Attempt missed. Andreas Christensen (Chelsea) header from the centre of the box is close, but misses to the left. Assisted by Marcos Alonso with a headed pass following a corner.
Corner, Chelsea. Conceded by Jasper Cillessen.
Attempt saved. Marcos Alonso (Chelsea) left footed shot from a difficult angle and long range on the right is saved in the top right corner.
Pedro (Chelsea) wins a free kick on the right wing.
Foul by José Gayá (Valencia).
Offside, Valencia. Gabriel Paulista tries a through ball, but Maxi Gómez is caught offside.
Substitution, Valencia. Mouctar Diakhaby replaces Denis Cheryshev.
Foul by César Azpilicueta (Chelsea).
Maxi Gómez (Valencia) wins a free kick in the defensive half.
Substitution, Valencia. Lee Kang-In replaces Rodrigo Moreno.
Olivier Giroud (Chelsea) is shown the yellow card for a bad foul.
Foul by Olivier Giroud (Chelsea).
Gabriel Paulista (Valencia) wins a free kick in the defensive half.
Foul by Pedro (Chelsea).
Daniel Parejo (Valencia) wins a free kick in the attacking half.
Penalty missed! Still Chelsea 0, Valencia 1. Ross Barkley (Chelsea) hits the bar with a right footed shot.
VAR Decision: Penalty Chelsea.
Penalty conceded by Daniel Wass (Valencia) with a hand ball in the penalty area.