One of the most difficult decisions a Head Coach/Manager needs to make is Matchday squad selection and starting XI, a manager not only considers opponents, but form of players, fitness, tactics and suitability, etc... and with all that, rotation becomes more trickier, and in Ten Hag's case, I see it more as tactics and suitability, which means certain players he can't afford to rest, like Bruno, Eriksen and Cas, they are too important to rest/rotate and their replacement (Fred, McTominay, VdB, Iqbal? etc...) are not good enough to start games except for Fred in certain games, Ten Hag does have some flexibility in CB/FB, where Malacia & AWB are doing well instead of Shaw & Dalot, also against smaller teams he can start with Maguire & Lindelof and rest Varane & Martinez, and in attack, Garnacho has become a serious option as a sub or as a starter in some games.