1. MIDFIELD THREE MISSING
Manchester City coasted to the title last season because they had the best midfield. Between them, Kevin de Bruyne, Fernandinho and David Silva either scored or assisted in 52 of City's 106 league goals. Silva missed 10 games because of his son's premature birth, so that total would have been higher.
This season, they have not started one league game together because of injury problems for de Bruyne and Silva, and most recently Fernandinho (above) as well.
What City have missed is a perfectly balanced midfield. They have one attacking left-footer (Silva), one attacking right-footer (de Bruyne) and, in Fernandinho, they have a destroyer who sits deep and protects.
City also miss David Silva because of his understanding with Leroy Sane down the left.
Bernardo Silva, with five goals, has performed well in de Bruyne's position but he is starting to feel the strain. He said: "It's the toughest time since I came here."
2. CANNOT DEFEND HIGH BALLS
City's inability to defend high balls in their box is a problem that manager Pep Guardiola has known about since his maiden season in England.
"It's difficult to defend against long balls. In Spain and Germany, it doesn't happen. I have to learn," said the former Barcelona and Bayern Munich boss.
Two years on, City's aerial struggles remain.
City have one of the shortest squads in the league. They have only five outfield players who are 1.85m or taller (Aymeric Laporte, Danilo, Sane, John Stones and Vincent Kompany). Given that Danilo and Kompany barely play, that leaves just three tall players in the team at any one time.
Some of City's costliest goals have come from high crosses into the box, such as Leicester's opener on Wednesday, David Luiz's header (above) in the defeat by Chelsea and Willy Boly's diving header in the 1-1 draw away to Wolverhampton Wanderers.
3. FULL-BACKS' POOR FORM
The return of Benjamin Mendy (above) from a serious knee injury was supposed to make City's defence complete again but the left-back position remains an area of weakness.
At the start of the season, the 24-year-old recorded five assists in his opening seven games but his form then dipped.
Guardiola has no like-for-like replacement for Mendy. Fabian Delph filled in adequately last season but this term he has not been as good, particularly when it comes to his positional discipline.
City have also struggled because they do not have adequate competition for Kyle Walker, the right-back.
Danilo has not played consistently well since joining from Real Madrid 18 months ago, so when Walker plays poorly - as he did against Crystal Palace - Guardiola can only bring in a far less mobile and effective replacement.
THE TIMES, LONDON