"The whole thing is a concern for us," said Grant. "We will be in contact with Wales and we will make sure Earnie has to stick to this work plan we have given him.
"The problem is I know what international football is like. You go away and sit in hotels and you say, 'Oh, I will do it tomorrow,' because everyone else is switched off.
"But Earnie has just come back from injury and it's a different sort of scenario.
"If he doesn't do the work plan we have set him, he won't be going. I don't care what anybody says, if Wales don't stick to the work plan that we are going to give him, then he's not going.
"It's great for Earnie if he is available and fit for Wales, but the biggest thing for us is we will be working through the summer to make sure he keeps where he is.
"You see the Michael Owen scenario - and Earnie is as important to us as Michael Owen is to England.
"He is too valuable as a person and he has worked too hard to get where he is for us to rush it," said Grant.
"You know what adrenalin does for you, it gives you that pump that you sense everything is great.
"The first 25 minutes is okay for him, but if you rush it over the next six games you can hardly move.
"He will be monitored very, very closely. We don't want a setback. He is ahead of schedule after the way he has worked his socks off.
"He has done exceptionally well to get there and we have to make sure we don't ruin that good work."