Savea, 27, wasn’t selected in the end-of-year squad, with Matt Duffie one of the wings picked ahead of him in a possible blow to his mindset.
But in an interview with Andrew Gourdie and Jim Kayes on RadioLIVE, Fox says the Wellington finisher know what he has to do to get back in.
“The ball’s in Juls’ court,” he said. “I think what Julian really needs is to have a really big off-season, get himself in the best possible shape. He can find his speed and agility again.
“He’s getting there, but we don’t think he’s quite there yet. I think a big off-season will help him do that.
“Super Rugby will be pretty critical to Juls’ All Blacks future next year.”
Fox has sympathy for Savea in that age might be catching up with him, adding: “As you get older, the speedsters often become a little bit of a problem for them; it becomes challenging.
“So he’s just got to plot his way through that. Whether that’s diet or losing a bit of weight, I don’t know – all sorts of things just to find that little bit of sharpness again and find the agility to beat players , find that little bit – maybe deeper aerobic fitness – to up their work rate a little bit.
“That all gets harder as athletes get older, no matter what position, so those are just areas he’s just got to keep chipping away at.”
He is also confident that time away from the squad could give Savea a new-found hunger that can only benefit both the player and All Blacks.
“Time away will help him rekindle that fire again – we often find that happens,” he added.
“You don’t sometimes appreciate what you’ve got till it’s not there anymore.”