Hazard returned late to Chelsea following Belgium's appearance in the latter stages of the World Cup, in which the winner played a pivotal role.
Since then, he has scored five goals in five games, and provided two assists to take Chelsea top of the Premier League table.
However, it appears he is not yet at 100% as the midweek trip is one step too far for the former Lille man at this early stage of the season.
"He told me that after the national team and after the match against Cardiff he was a little bit tired," Sarri said.
"I thought it was better to stay in Cobham, to have training and to rest."
David Luiz is also remaining in London, but Ruben Loftus-Cheek could see his first serious minutes of the season.