Valencia gate-crashed Frank Lampard's managerial bow in the Champions League by earning a 1-0 win at Chelsea on Tuesday after Ross Barkley spurned a chance to equalise by missing a penalty three minutes from time.
Barkley took the penalty after a debate with Jorginho and Willian but missed as Chelsea fell to defeat.
"I don't know what the conversation was, but Jorginho and Willian were the takers on the pitch. When Ross comes on, he becomes the penalty taker and he missed it," Lampard said after the game.
Barkley, who came off the bench in the 80th minute, said: "[They were] more just encouraging [me] to score the goal. Obviously they are confident to take the penalties as well but I practice penalties every day.
"I don't miss them in training and in preseason I scored penalties. I've missed penalties before when I was at Everton and it is one of those things. I'm gutted that I missed but these things happen.
"We've got a lot of good penalty takers in the squad and on a sheet in the changing rooms it says I'm on penalties if I'm on the pitch.
"Otherwise, its Jorginho. But all players, sometimes you feel confident to take them on but we can all miss one."
Spain forward Rodrigo Moreno gave the visitors the lead against the run of play in the 74th minute of the Group H game, getting the slightest of touches on a free kick from Dani Parejo to send the ball into the roof of the net.
Chelsea continued to threaten and were awarded a penalty after a VAR review spotted a handball by Valencia defender Daniel Wass.
But Barkley sent the resulting spot kick onto the bar and over and Europa League holders Chelsea fell to their first home defeat in European competition since losing to Paris Saint-Germain in March 2016.
"We shouldn't lose the game. Clearly," Lampard told reporters.
"We had a fair few chances and then the penalty, which we miss. We have to keep our heads up. There is a long way to go and this is a lesson that teams at this level can hurt you."
Lampard added: "The disappointment to all of us is that we didn't get chance to win the game. There is no issue in the dressing room."
Lampard became the first Chelsea manager to lose his debut Champions League match in charge -- 10 of the previous 11 had won, while Gianluca Vialli drew with AC Milan in 1999.
Valencia travelled to London reeling from a stinging 5-2 league loss at Barcelona in coach Albert Celades' first game in charge after the much-loved Marcelino was sacked, despite overseeing two top-four finishes and winning the Copa del Rey.
His dismissal bewildered the players, who began a media blackout after the decision, while influential defender Ezequiel Garay fiercely criticised the move in an angry post on social media.
But the Spanish side lefy the English capital emboldened and with three points after producing a solid, professional display and celebrating their triumph with their small band of travelling supporters tucked in a corner of Stamford Bridge.
"It's difficult to forget about everything that has happened but I thank the players for welcoming me and their professionalism," Celades said.
"We are going to get back to normality little by little and I was hugely impressed by the effort we put in today. It was not the ideal situation but we have tried to close ranks and look forward."
Parejo was the only Valencia player to publicly speak after the match, saying they'll now support Celades.
"Football is like that. I've had a lot of managers. It's true that [Marcelino] did a great job here and his name will be in the history of Valencia but now another coach has arrived and we are with him to the death as our job is to win and give everything in the pitch," he said.
"Now it is a new era, with a new manager and our goals are the same, going out to win every game and of course we are to death with the coach. "
Lampard's side went into the game in a confident mood after beating Wolverhampton Wanderers 5-2 in the Premier League on Saturday and their supporters belted out the manager's name in his first Champions League game as a coach, after he won the competition in 2012 as a Chelsea player.
The Dutchman then twice thwarted Marcos Alonso, parrying a low free kick early in the second half and tipping another set-piece effort from the Spaniard over the bar in stoppage time.
"It did affect the game and we know how well he is playing," Lampard said of Mount's exit. "He looked sharp. It is an ankle injury and hopefully not too bad. It needs to be assessed over the next few days."