No wonder Pep Guardiola stood motionless on the touchline as Manchester City fans booed the latest disappointment in a rapidly unravelling title defence.

He arrived at the Etihad on Boxing Day with just 12 senior outfield players, with two benched due to a virus. The ten players he fielded were the only ten he had available - not the first time he has had no alternative options this season. Kyle Walker and Jack Grealish joined Ederson, Ruben Dias, John Stones and Matheus Nunes on the short-term injury list, making it eight players out.

Walker and Grealish were the 88th and 89th players to be unavailable to start through injury, fitness or suspension this season in the Premier League after just 18 games. That is the same figure as the whole of last season across 38 games - Guardiola is, in some ways, helpless to watching the team he built crumble before his eyes due to factors he simply cannot control.

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If each player available to Guardiola for each game is an individual selection decision for the manager to make, then subtracting those enforced absences can paint a picture of how hampered City have been this term.

Last season, ten per cent of Guardiola's possible selection decisions were unavailable, an unhelpful but manageable number. This season, that figure has gone up by 120 per cent.

An average of 22 per cent of Guardiola's squad have been unavailable for games this season. Sometimes it has been considerably higher. He will not have a fully fit squad all season, and he has been crunching the numbers as to why injuries have shot up so dramatically.

Every possible explanation for one win in 13 comes back to the injuries. There are very valid questions to be raised over form, transfer strategy, individual players or selection calls, but each one is exacerbated by the fact that so many key players are out.

But why are so many players suddenly getting injured so quickly?

"Basically because we didn't have training during many months," Guardiola replied to that very question this week. "The lack of training for many players is a lot, demanding so high. The body cannot sustain the amount of actions and energy we have to do when you are not well prepared."

Some injuries are easily explained. A freak incident broke Oscar Bobb's leg, while a contact injury injured Rodri's knee. Most issues, however, have been muscular.

In a way, City are victims of their own success. Year upon year of going deep into four competitions takes it's toll. Phil Foden, Rodri and Kyle Walker have spoken of burnout, added to by international success for Spain and England. Mentally and physically, playing in the very best teams in the world has caught up with them.

"The muscles normally when you demand the same effort from your body and your body is not prepared. It's just one reason, we cannot have training," Guardiola continued.

"We had five players on the tour. After the guys that come back, we didn't have back four all defenders together this season once [in training]. Not trained once.

"When players in that period all together have 100 less training sessions than the treble year combined all year in that period in November. That is the reason why. People say why injuries? The schedule basically, then many years together and a lack of preparation."

Players who aren't injured are then playing more as a result. And those who need time to return to full fitness are being rushed back before they can properly train, resulting in them breaking down quickly - look at John Stones.

The boss added: "They have to play. One game is fine. Then another game in three days and three days another one. They cannot sustain it for much longer. I'm not a doctor but when you demand your bodies the effort and your body isn't prepared you get injured."

A rough estimate suggests City have been able to train between 40-50 times this season, not including recovery sessions, and depending on how much time off Guardiola has granted. Of those possible sessions, the distribution is heavily weighted to the four weeks in August without midweek fixtures.

Since September and the Champions League, the opportunity for training has shot down. When Guardiola has been able to get on the training pitch, the condition of his players and limited numbers means he has been unable to get much done. He is in an endless injury cycle that only only end with fewer fixtures and more training.

The injuries don't explain City's woeful defending, or their inability to keep a clean sheet, or lack of confidence to supply Erling Haaland. But the context of 100 lost sessions and the defensive crisis contextualises a problem critics have quickly ignored.

Even a genius with Guardiola's record cannot operate with an unfit, lopsided squad running on empty.