Everton boss Ronald Koeman feels his old friend Pep Guardiola may well have underestimated the physical intensity of the Premier League.
Guardiola arrived at Manchester City as manager last summer having won LaLiga in three seasons out of four in charge at Barcelona and then the Bundesliga in three out of three as Bayern Munich boss.
City made a superb start under the Spaniard, leading the Premier League with maximum points after six games.
But the record since then has been seven wins from 14 matches, and ahead of this weekend's round of fixtures - which sees them face Everton away on Sunday - City were fourth in the table.
Asked if he thought his former Barca team-mate Guardiola had found English football tougher than anticipated, Koeman, who had two years at Southampton before switching to Everton last June, said: "Maybe, yes.
"But I think to see what happens in the Premier League, you need to be part of that. Then you realise how difficult it is.
"Maybe the way he likes to play, against the physical intensity of the Premier League, is more difficult."
City - who drew 1-1 with Everton at the Etihad Stadium in the reverse fixture in October - head into this contest having thrashed West Ham 5-0 in FA Cup third round last time out.
Everton, in contrast, were dumped out of the competition as they suffered a 2-1 home defeat to Leicester.
Koeman is glad for the chance to bounce back in such a high-profile game.
"We know we had a really big disappointment last week," the Dutchman said.
"Now we have an opportunity after that defeat.
"We know we need to be very good. They had a great performance last week against West Ham.
"But if we go face-to-face on Sunday, and we play with that aggression and pressing, then we can make it very difficult."
Everton were eliminated at home in both the FA Cup and EFL Cup this season, but Koeman has pointed out that in the league his team - seventh at the start of the weekend - have been beaten only once so far at Goodison Park, last month's 1-0 defeat to Liverpool sealed by Sadio Mane's added-time goal.
"So far, we have lost one game in the derby after something like 95 minutes - everybody knows it is difficult to beat Everton at home," he said.
Koeman has confirmed new signing Morgan Schneiderlin, who joined from Manchester United on Thursday, will be part of the Toffees matchday squad on Sunday, and says there is a chance another recent arrival, Ademola Lookman, could also be involved for the first time after he was cup-tied for the Leicester game.
Maarten Stekelenburg and James McCarthy have been back in training after a dead leg and hamstring injury respectively and Koeman will make a late decision on whether they are fit enough to start, while Aaron Lennon is available again after a knock.