Chelsea manager Maurizio Sarri has attacked his players again after the 4-0 defeat to Bournemouth on Wednesday, also questioning his own ability to motivate the squad.
The Blues had the chance to move clear of Manchester United in the race for Champions League qualification but the heavy loss instead meant their spot in the top four was taken by Arsenal.
Speaking after the game, the former Napoli boss again said he may not able to coerce consistent performances out of his players.
He said, as quoted by Sky Sports: "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."
Cherries goalkeeper Artur Boruc denied both Cesar Azpilicueta and Mateo Kovacic before the hosts ran riot, Josh King scoring twice alongside David Brooks and Charlie Daniels' strikes, and Sarri admitted his team has lost its way in recent weeks.
He 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."