The City boss admitted his squad has been caught up by rivals, with fatigue and aging players contributing to their decline.
After leading the table in November, City have since slumped and are now battling to secure a Champions League spot.
"It’s a big question mark. I would like to give an answer but it is a big question mark and I would say not a positive feeling because we are in the position we are," he said about the upcoming Club World Cup.
"We changed some things but it is the same medical staff and same methods in training. You can change the manager or staff and immediately get injuries, injuries, injuries - and there is a relation. But this is more the age and the cumulation of seasons and seasons. In the end, my analysis of that is so simple - the body speaks for itself and says: ‘It’s enough. Give me the heart to play, but the body says I need a rest. Otherwise I will get injured'.
"We cannot rest. We have had this in the past and have handled it. Kevin (De Bruyne) has played one of the most amount of games for a player in the last eight or nine years, playing every three days and making an incredible effort with the distances he runs and the physicality, attacking the channels, regained the ball with Fernandinho and Rodri passing to him and run and go.
"He could do it and now he’s 33 years old and has come from five months injured last season, he’s not the same. The body was injured five months, afterwards I would go on holiday, but they go to a national team to play a World Cup.
"Oh, there is a new competition from UEFA, the Conference, now with the Club World Cup. It's not all about the managers or the physios, it's just this amount of games and the bodies of the players saying I'm tired."