Cape Town - Chelsea boss Jose Mourinho sprung to the defence of new goalkeeper Asmir Begovic after the Bosnian conceded four goals against the New York Red Bulls after coming on as a halftime substitute in a friendly on Wednesday.
Begovic, signed from Stoke City this month for £8 million as competition for first-choice keeper Thibaut Courtois, was introduced with the English champions 1-0 ahead in New Jersey but Chelsea ended up losing 4-2.
"He was very tired, the same as Courtois. When the goalkeepers are very tired the coordination is low, the agility doesn't exist and the speed of reaction doesn't exist," Mourinho told reporters.
"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 (Paris St Germain) he will start. He will play the first half.
"There's no problem, it's just a process."
Loic Remy had given Chelsea the lead but Franklin Castellanos equalised before 16-year-old Tyler Adams put the hosts ahead and Sean Davis scored twice.
Eden Hazard was also on target for Chelsea in the first game of the club's three-match tour of North America.
"I was surprised by our fragilities," Mourinho added.
"I was surprised that we were not good enough in the second half to cope with that."
The Premier League season begins on August 8.