Chelsea have recently been starting matches slowly, and Maurizio Sarri is unsure why this is the case.
The west London club were held to a 0-0 draw by Everton at Stamford Bridge on Sunday and after the match, Sarri bemoaned his Blues’ sluggish start to games.
"I didn't like the first 25 minutes, we moved the ball too slow, it was too easy for them to defend," Sarri told a news conference.
"Then I think we have played a very good match in the first part of the second half, for 40 minutes. We were a bit unlucky. I think we are in the right way.
"I don't know [why Chelsea start slowly], it's difficult to answer.
"I don't think it is a physical problem, in the second half we played at another speed, intensity, so I don't think it is physical, maybe mental.
"We have some difficulties to approach from a mental point of view."
Sarri has a new managerial record for the best unbeaten run from the start of a Premier League career after the Blues made it 12 matches without a defeat in the top flight on Sunday.