Pep Guardiola has expressed concern that Manchester City could stumble significantly in the New Year as they chase success in four competitions.
The City manager is worried that he does not have the experience to cope with the kind of schedule his side are likely to face over the next couple of months.
Guardiola's side have been in extraordinary form over the first half of the season, dropping just two points in 20 Premier League matches.
They also finished top of their Champions League group, securing a last-16 tie against Swiss champions Basel in February.
But City have faced nine matches during a busy December, and are set to play a minimum of seven during January, with four fixtures in the Premier League, a two-legged League Cup semi-final against Championship side Bristol City and an FA Cup third round home tie against Burnley.
Victory over Burnley would ensure another cup game at the end of January, and Guardiola is concerned that the schedule will eventually catch up with his players.
"Handling four competitions, I don't know if we will be able to do that," he said.
"When I look at the schedule, we have to be careful. So I am worried. I am worried because we cannot play every three days.
"After Crystal Palace and Watford in the Premier League, we have the FA Cup against Burnley, and then the League Cup against Bristol City, who have taken out four Premier League teams. So be careful.
"Kevin de Bruyne cannot play every minute every three days. The players need refreshing to be right for the last part of the season.
"Also, I never lived in that situation before. Three competitions, I've handled many times. But four, never. And the fourth competition is not one game.
"It's double games and (potential) extra-time. So that's why I am worried. We are going to see how we handle that situation."
Guardiola's predecessor, Manuel Pellegrini, faced similar problems two seasons ago, when City were still in four competitions in February, and ended up effectively sacrificing the FA Cup by fielding a side of fringe players and youth-team graduates for a 5-1 fifth-round defeat at Chelsea.
- 'Real leader' -
City arguably have more depth in their squad now, with Guardiola allowed to invest heavily since replacing Pellegrini in July 2016.
That investment is now paying off, with City looking set to run away with the domestic title, and in contention to complete the quadruple of Champions League, Premier League, FA Cup and Carabao Cup, something which has never been achieved by any English club.
Guardiola, though, takes little satisfaction from City's outstanding recent form, instead suggesting that it has made him question why they did not do better last season.
Their success to date has been achieving with the bulk of last season's squad; of the players he brought in last summer, only goalkeeper Ederson and right-back Kyle Walker have been regular starters.
"When I speak with my staff, I say that we are playing with nine players from last season," Guardiola said.
"So something we did last season was not good. There was something we missed.
"Of course they know us, the staff, better and we know them better. Last season, for example, I never thought we would play Fabian Delph at full-back.
"Now it's: 'Ah, the brilliant Pep. How talented he is.' Why didn't I do that last season? I ask myself as well.
"Sometimes you need more time to see things. He's a real leader in the locker room is Fabian Delph.
"That's why I always give credit to the players for what they do."