Pep Guardiola would dismiss any suggestion that he has a strongest Manchester City XI with ill-disguised contempt. The notion that he has a fixed “strongest team” in his head is not only an attempt at pigeon-holing his players, it would also be disastrous for squad morale.
Guardiola has made it plain that a strong showing in training can alter his perception, and from there the selection, of his team for any given match. The message to all of his players is a valuable one - give your all in training, and you could force your way into the side at any given moment, and any easing-off could have the opposite effect.
The strength of City has been the depth of quality in the squad, even though in terms of numbers it is one of the smallest groups in the Premier League. That allows for rotation without a noticeable drop in standard, and explains why the Blues have been able to roll through long winning sequences that go from midweek to weekend to midweek, without any let-up.