Maurizio Sarri thought Chelsea would have encountered problems before now, as the Blues prepare for the visit of Premier League leaders Manchester City.
The Italian was appointed in July after compatriot Antonio Conte was sacked following the Bluesâ fifth-placed finish last season, 30 points behind champions City.
Chelsea enjoyed an 18-match unbeaten start to the competitive season, after losing the Community Shield to City in Sarriâs first game in charge.
Two defeats in the last three league games, to Tottenham and Wolves, mean Chelsea sit fourth, 10 points adrift of leaders City after 15 games.
âI was sure that sooner or later weâd face problems, but I thought it would be in the first two months,â Sarri said.
âThe first two months we played well, we gained points. And so I thought that the problems would arrive in November and December. I was sure.
âWhen you change the way of playing, the way of football, you need to change the mentality. You need to change the mentality in 25 minds, so itâs not a short way. Itâs very difficult.â
Pep Guardiolaâs City have won 13 of their Premier League games and are unbeaten in the top flight since April.
Sarri, who has experienced defeat to Guardiola with Napoli and Chelsea, was asked how his side can beat City.
He added: âAgainst Guardiola I lost every match, so I donât know. You have to ask somebody else.â
City are the best team in Europe, Sarri says â and that is his target for the Blues. He added: âItâs a very difficult match against, maybe, the best team in Europe at the moment.
âItâs impossible to beat them in a long period, of course, in this moment. But in a match, everything can happen.
âIn 90 minutes anything can happen. We know itâs very difficult but we have to believe in it.â
Sarri accused his Chelsea players of a collective âblackoutâ at the first sign of trouble against Fulham, despite a 2-0 win, and against Wolves.
The Italian said: âWe have a problem to manage the match at the moment. In the last two matches we played well for 55, 60 minutes, then the first difficulty we went in blackout.
âIn the first match (against Fulham) we were lucky because they didnât score. In the last match (at Wolves) we were a little bit unlucky. For the opponents, five shots, only two on target. We conceded two goals.â
Sarri has been criticised for his use of NâGolo Kante.
Sarri struggled to explain the reason for the lapses.
He added: âItâs not really very easy to answer. We didnât react as a team (but) as 11 players. In 11 different ways. So itâs a big problem. We were not able to have the right determination to win the match.â
Playmaker Jorginho is expected to return after being rested against Wolves. Sarriâs selection of Jorginho at the base of his central midfield, with NâGolo Kante further forward, has been scrutinised.
The Blues boss has explained his reasoning and says the choice is only being questioned due to the defeats.
Sarri added: âThe problem is only the results. When we won, the position of NâGolo was âgoodâ. So itâs only down to the results.
âAt the moment, weâre not winning so itâs normal that some players are playing very badly, some players are in the wrong position.
âI explained why, usually, Kante plays in that position. I have my opinion. I can understand that you or someone else doesnât agree. But I explained very well why.â