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.

Asmir Begovic endured a disappointing Chelsea debut. Elsa/Getty Images

"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."