The Foxes are likely to be without England stars Jamie Vardy and Harry Maguire, but United could be missing seven of their own players.
Paul Pogba, Romelu Lukaku, Phil Jones, Jesse Lingard, Marcus Rashford, Ashley Young and Marouane Fellaini all went deep into the tournament and both teams are planning to give all the aforementioned squad members at least three weeks off to rest and recharge.
“Three weeks (off), which I think is the minimum that their body and soul needs, and which is the minimum for them to return and think about football again,” United boss Jose Mourinho told Russia Today (H/T LeicestershireLive).
“To bring them back before that would be, ‘OK I have you for the first match of the season but maybe I don’t have you in three of four months'.
“I think three weeks is the minimum they need. Which means that they’re going to be back in the week when the Premier League starts.
"Which means they’re not ready to start the Premier League, which is I think difficult to understand, where we could have one more week to prepare everybody.”
Maguire played all but 45 minutes of England's seven matches, but a groin problem saw Vardy's minutes limited. The Three Lions squad are expected back in England on Sunday after having played their final match on Saturday.