United start their 2018/19 season against Leicester on August 10 - just four weeks after the World Cup.
Man Utd boss Jose Mourinho told RT while a guest pundit: “We cannot start the Premier League with our players that were in the World Cup, which is a shame for the most important club competition in Europe.”
Mourinho said it was 'a shame' that these players would miss the opening day match at Old Trafford, but said the short window did not allow sufficient time for players who had featured at the World Cup in Russia to rest and then recover their fitness.
A number of Manchester United players progressed into some of the final rounds of the World Cup this summer, with midfielder Paul Pogba set to contest the final for France against Croatia.
Jesse Lingard, Marcus Rashford, Phil Jones, Ashley Young, Romelu Lukaku and Marouane Fellaini were all represented in the third place playoff on Saturday between England and Belgium.
Mourinho told RT he would give his players three weeks off following their World Cup commitments, meaning many will not have completed the necessary pre-season preparations to start on opening day.
Mourinho said: “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.
“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.”
David de Gea, Victor Lindelof, Marcos Rojo and Nemanja Matic were the other Manchester United players to feature at the World Cup.
Opponents Leicester City had 10 players represented at the World Cup finals in Russia. It is unclear how long the Foxes intend to rest their players, and if they will be missing from the opening day squads too.