The Dutchman is fully fit and back to his best after missing nearly all of last season with a serious knee injury.
Van Dijk did not play for the Reds against AC Milan in a 3-2 Champions League group stage win in midweek.
"We all think Virg is Superman and he is, 99 times out of 100," said Milner, per Sky Sports.
"But the injury that he has come back from - and to look as good as he has done since he has come back - you know, he's not 21.
"To do what he has done since he's been back is incredible. It shows what a good player he is, what a mentality he has.
"But he needs looking after as well, no matter how angry he gets at being left out of the team. He is going to need looking after and that is rotation."
Milner added: "You look at the centre-halves in the club - they are all incredible. You see them in training, they are unbelievable.
"I think it (rotation) is obviously important. The positions we got into last year, we were unlucky with injuries and players having to play out of position. I think it is to help with things like that."
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