Pep Guardiola was asked if this season is a survival of the fittest and whether the champions would end up being the team who gets the least players injured, or at least the least number of key players injured, reports BBC Sport.
Guardiola said he didn't have the answer to that but: "It's impossible.
"To demand they are fit for 11 months playing every three days is impossible.
"There are injuries at all the clubs. We knew it and we have tried to avoid it by taking better medical care of the players. But they are human beings. With this amount of competitions, the body says it's enough.
"When we demanded five substitutions, it's for this reason. Why can we do it in the FA Cup but not the other competitions.
"I'm not just saying it because it's Kevin. It's too many games and competitions, in the end, the players suffer."