Chelsea boss Jose Mourinho said there was "no problem" with Asmir Begovic after the goalkeeper conceded four goals against New York Red Bulls.
Begovic, who signed from Stoke earlier this month, made his first Chelsea appearance as a half-time replacement for Thibaut Courtois when the score was 1-0 to the English champions.
Chelsea ended up losing the game 4-2 after a second-half collapse, but Mourinho defended the 28-year-old keeper.
"He was very tired, the same as Courtois," Mourinho said on the club's official website. "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 [on Saturday] he will start. He will play the first half. There's no problem -- it's just a process."
Mourinho did express some disappointment with the performance but pointed to his players' lack of fitness and suggested the MLS side's players may have had more motivation to win the friendly.
"I said before we have no fragilities but today we had fragilities, lots of fragilities," he said. "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."
He added: "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 preseason matches is to play, to run, to bring intensity back, so no problem. 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, maybe better than they should, but a very good match. They are not going to forget they beat Chelsea, even if it was preseason."
Mourinho also gave Burkina Faso international Bertrand Traore some game time and he said the winger, who spent last season on loan at Vitesse Arnhem, would remain at Stamford Bridge this season.
"He's 19, he's a kid," he said. "He was in Africa, then Vitesse, and now he's at Chelsea. He's not going on loan. We want to keep him and improve him.
"With the ball he has a lot of talent. Sometimes he didn't always make the best decisions, but this is absolutely normal. He's a good kid, a good talent, and I repeat he's not going on loan."
Victor Moses, who has spent the last two seasons on loan at Liverpool and Stoke, was also given a chance to play against the Red Bulls.
"Victor is strong, he's experienced and he knows the Premier League well," he said. "He's fast and aggressive. Okay, he has to learn how to play with us but I'm happy with his week and his 45 minutes."
Stoke boss Mark Hughes said earlier this month that he did not expect to re-sign Moses as he thought he was now in Mourinho's plans, but the Chelsea boss remained coy on the Nigeria international.
"Let's see what happens but Victor had an evolution in the last couple of years," he said.