Everton boss Frank Lampard was left stunned by their 4-0 preseason defeat to Minnesota United.
Everton secured Premier League safety last season with a win against Crystal Palace in their penultimate game.
"The players have to understand that we were in a relegation battle for a big portion of last season," said Lampard.
"We had an amazing night [against Palace] and an amazing run which was great historically for the club but, as soon as that finished, I put it to bed very quickly so the players better put it to bed as well.
"We were in that fight for a reason and, if we don't want to be in that situation again, they have to be better, I have to be better."
Everton's defeat by Major League Soccer side Minnesota United followed a 2-0 loss to Arsenal in the first game of their US tour.
They play at Blackpool and host Ukrainian side Dynamo Kyiv in further pre-season games before starting their league campaign at home to Chelsea on 6 August.
"Lots to think about, lots of work to do," said Lampard. "What matters is where we are at in two and a half weeks.
"If there is to be good to come out of this, the players and the dressing room have to understand that they have just put in a very poor performance individually and collectively and been well beaten."
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