Jose Mourinho admitted Chelsea were "not good enough" as they crashed to defeat on the opening game of their summer tour of the United States.
The Premier League champions were beaten 4-2 by New York Red Bulls who scored all their goals in the second half.
Loic Remy had given Chelsea the lead before the MLS team struck back after the break leaving manager Mourinho to say: "I was surprised by our fragilities.
"I said before we have no fragilities but today we had fragilities, lots of fragilities. I was surprised that we were not good enough in the second half to cope with that.
"We hit the post two or three times. I don't know but they're young guys, they have quality, and motivation, and their motivation is really high to play against us."
Despite the defeat, Mourinho welcomed the challenge presented to his players in preparation for the coming season.
We needed to play better than we did in the second half defensively, and there were also too many missed chances.
He told the Chelsea website: “They gave us a good training session. If we came here and won 10-0 I would not be happy because it would mean it was too easy. We needed the game they gave us.
“Obviously we needed to play better than we did in the second half defensively, and there were also too many missed chances but the intention of pre-season matches is to play, to run, to bring intensity back, so no problem.
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“We are a top team, we have top players. We only started training six days ago. The kids that played for Red Bulls were very good opponents for us: sharp, quick, fast, and highly motivated. I believe they were so happy to play against Chelsea.
“They gave us a good match. They are not going to forget they beat Chelsea, even if it was pre-season.”
He also accepted that it would take new goalkeeper Asmir Begovic time to get up to speed at his new club.
“He was very tired," added Mourinho. "When the goalkeepers are very tired the coordination is low, the agility doesn’t exist, and the speed of reaction doesn’t exist.
“Courtois made a mistake in the first half with the ball at his feet. Begovic in the second half was not sharp in his reactions but it’s a consequence of being tired from training.
“I’m so happy to have him and in the next game against PSG he will start. He will play the first half. There’s no problem, it’s just a process.”