Jose Mourinho admits Manchester United's preparation for the derby with Manchester City will be hampered by the international break.
A large proportion of the United squad will be away with their respective national teams over the next week.
Mourinho is troubled by not being able to monitor how his players train and live during this period, with his concerns heightened ahead of the match with rivals City on September 10 that pits him against Pep Guardiola once again.
"We keep eight outfield players and Sam Johnstone as the goalkeeper [for training]," the manager told MUTV.
"We are going to lose the others and we don't know the way they train, the way they recover, the life they are going to have with their national teams.
"Some are coming back on the Monday before the Manchester City match but some are coming back on Friday. The day before Man City, we will still have Sergio Romero, Marcos Rojo and Antonio Valencia arriving.
"It will be a complicated process but we know it is like this when we have these players. And I would love all of the players to go because it would mean that everybody is being selected for their national teams."
Zlatan Ibrahimovic has made a sensational start to his United career, scoring three goals in as many Premier League appearances and netting the decisive strike in the Community Shield win against Leicester City.
The 34-year-old Swede, who retired from international football after Euro 2016, will be given an additional two days rest compared to the rest of the squad.
"I give the other guys, who are not selected for the national teams, two days off," said Mourinho.
"And I give four days to Zlatan. At 34 years old, you need to rest."
