"We are together and all together, we are disappointed," Ten Hag said on the club's website. "It should not happen. And, yeah, we have to take the responsibility together.
"I think we didn't start well and we already had a warning shot, when they almost had a penalty. That should have woken us up. But then we gave a goal away very easily.
"And then you make them big because they are a transition team and they defended very tough. They go in the duels, they go one-on-one and it was very difficult then. I thought we played too but we didn't have the brilliance in the box."
Man Utd have some big matches coming up, including a trip to face Premier League leaders Liverpool next weekend and Ten Hag acknowledged his team need to put things right.
"First, we have to put this in the right place," Ten Hag said. "And of course we know what is coming up and we have to do things better. And as you said, the difference between the start against Chelsea and today was massive and that shouldn't happen."
"It’s been consistently like this when we win a game, [in] the next one we don’t perform," he told the club's official website. "We don’t perform the same way we did before.
"I don’t know if it’s a lack of concentration or focus or something else, but it is something we have to be aware of after winning a game.
"We have to get that consistency of winning games, even sometimes [if we are] underperforming, but getting the result."