The visitors had just three shots on target throughout the game, but the Toffees boss was far from happy with his team's defensive display.
Speaking to reporters after the game, Martinez said: "Looking at the stats there's something spooky about it. They had three shots on target with three goals. There were three individual errors and as a team that's hard to swallow.
"The defensive intensity was back with us in the last two performances but today we were trying to chase the game. That left us without the focus and concentration we need to have because they were very uncharacteristic errors today and we were heavily punished.
"I don't see it as a [long-term] problem as the last two performances were back to our defensive standards that we have as a team."
Everton travel to Anfield to face local rivals Liverpool next weekend.