The Italian accused his players of being difficult to motivate after the 2-0 defeat by Arsenal in their previous Premier League game, and again questioned the desire of his players as they suffered a fifth league loss of the season.
Sarri said: “I am not able to explain because we played very well in the first half. We conceded the goal very early in the second half but we had 43 minutes so all we needed to do was to continue to play.
“Maybe it’s my fault because maybe I’m not able to motivate this group and these players. I don’t know why. But I need to understand and we need to understand very soon because we have to play in three days.
“We are doing something wrong with our mentality, of course. We need to understand why and we need to react to the difficulty. For me it’s really difficult to understand why. I’m trying to do it, and I will try to do it tomorrow but it’s not easy.”
Chelsea missed good opportunities in the first half as Artur Boruc denied both Mateo Kovacic and Cesar Azpilicueta, but they were second best thereafter as Bournemouth capitalised on slack defending to inflict the heaviest league defeat on the Blues in 23 years.
It means that Chelsea have won 47 points after 24 games this season – three fewer than at this stage in the 2017/18 campaign, and a reaction will be demanded when Huddersfield visit Stamford Bridge at the weekend.
Sarri added: “If you stop playing, you can concede four or five goals. We stopped playing as a team and we stopped defending. We were in trouble but it was only a consequence [of our performance].
“At the end of the first half it was impossible to think the second would be a disaster and I want to understand why.
“Just like two months ago when we had to face difficulties, we lost our identity and played as 11 individuals.”