I think Dave simply does it because it’s the “plan” and the in game conditions are irrelevant to his pre-determined timing of substitutions. That has to be it. He subs and manages minutes for a young group like he has an older group. Fox’s kneecaps will fall off if he is stretched to closer to 40 minutes if he’s the only one making things happened. Better to watch Willie aimlessly stand in the high post contemplating one of his priceless drives or a pas while the pace, efficiently and the lead dies