The reason we have these injuries is the lack of alternatives. Overplaying our players will lead to recurring muscle injuries.
I think the intensity of the style and the players' injury-proneness is a bigger factor than lack of rotations. Most injuries are of players that get plenty of rest(Saele, Samu, Leao, Rebic, Conti, Gabbia, Tonali, Duarte, Musa).
Bennacer is usually the one who's rested when Tonali plays.
Calabria seems to incur more injuries when he's rotating with Conti/Abate than when he's the undisputed starter.
Ibra would threaten to retire if he's rested or subbed off against his will.
But yeah, Kjaer needs to be rested more frequently when he returns, and we need one more dependable defensive midfielder who can cover for Kessie/Bennacer in league games.