The Toffees were beaten 2-0 at Stamford Bridge, though O'Brien insists the scoreline didn't reflect the course of the game.
"A very disappointing result, but I think our performance wasn't that bad,” explained O’Brien, speaking after the game. “I think at times we played well, and we created chances and, on another day, we take them.
"We just gave them two goals at the start and it kind of killed us for the rest of the game.
“I mean, we'll go back and look at it. I think we got in good positions and, as I said, on another day, we take them and it’s a whole different game.
“But, yes, the performance wasn't bad today. I'm disappointed by the result, but I think there are positives to take from the result today. We can bring that into next week.”
The Toffees have now taken wins in five of their past seven outings.
“It's where we want to be,” added O’Brien. “And it's these types of games that it's disappointing because we can move on up the table again.
“But there's loads of games coming up and I think it's important that we're going into them positive and knowing that we can get results and points from them.”