Liam Rosenior described on Saturday evening as “the most disappointing evening so far” as his side succumbed to a fourth consecutive defeat.
Two goals from Beto and a third from Iliman Ndiaye moved the Toffees within two points of Chelsea, who stay sixth having missed the chance to move into the top four.
Robert Sanchez was culpable for the second Beto goal having early got away with a sloppy mistake with the game goalless.
The defeat comes four days after Chelsea exited the Champions League in an 8-2 aggregate loss to PSG.
"The most disappointing evening so far in terms of the things we've spoken about, not gifting goals away, making sure we're in the game, getting control of the game. It wasn't there and it turned into a really, really difficult evening where the result and performance was nowhere near what we expected or wanted," Rosenior said.
The Chelsea boss admitted to Your Site that he is still learning but tried to offer perspective. "I'm learning about this club. It's a massive club. There's been a lot of noise, a lot of negative noise, rightfully so, our performances in the last week.
"We've had 10 games in the league together as a group. We've got 17 points. I think we're fourth in my time. So we have to forget the noise. We have to keep our confidence and our composure."
Speaking in the press conference afterwards, Rosenior rejected the notion that his team's tactics were an issue. "It is not a tactical thing," he said.
"I want to protect my players always. I always will. I take responsibility for that lapse in concentration. But that's what it is. That's happened too many times in my time recently for me not to tell the truth as it is."
He explained: "For me, we arrived into the final third a lot. We had an edgy start in terms of cheap giveaways that we gave away, then we managed to gain control of the game and were in their half and we were arriving and creating moments which we don't take. We're not clinical enough. Then out of nowhere, it feels like out of nowhere, they score. It's not the first time that that's happened.
"What happens in football, if you are in a run, a difficult run of games against big teams, your energy levels and your confidence levels can drop if the other team score first. That's what happened. [Jordan] Pickford makes a world-class save at 1-0.
"Then we come out in the second half and have control of the game. Then we make a mistake and they're 2-0 up. It gives them even more energy. It's about flow and momentum. We didn't have that in the game today."
Asked whether the players are trying, Rosenior said: "For me, I don't think there's a lack of effort. I don't think there's a lack of belief or determination in the team.
"I'm aware when you're on a run of defeats that we're on and when you're on a run of performances that we've had, those things get levelled at you. But I don't think that's the issue in this moment."
Another theory that has been floated is that the players are feeling the effects of a long season having competed in the Club World Cup in the United States over the summer.
"What I don't want to do, I don't want to be seen to make excuses. That was not good enough. The last week hasn't been good enough.
"I think if you're a logical thinking person and you look at the workload and the amount of games that the players have played, I think it's a pretty simple conclusion to come to."
Whether Chelsea supporters will accept that with their side now having won only one of their last six Premier League matches is another matter.
"They pay their money, they love this club and they've come a long way. It's a disappointing time for the club at the moment in terms of the way we lost in the Champions League and the way we've lost the last two games.
"My job - it hurts, regardless of your position, it hurts to lose games of football - in terms of moving forward and having this time is to look at the bigger picture.
"We're one point away from the Champions League position. We need to keep working in this way. We need to keep giving the players as much confidence as possible and hopefully this break of games now for us comes at a really, really good moment."
