The Red Devils have already waved goodbye to Adnan Januzaj and Guillermo Varela on temporary deals, while questions still remain over the futures of Cameron Borthwick-Jackson, Timothy Fosu-Mensah, James Wilson, James Weir and Sam Johnstone.
With no emergency-loan window in operation this season, Joyce now believes that more Red Devils stars of the future could be on their way out of the door over the next fortnight.
"I would imagine, over the coming weeks, a few more will leave on loan," he told the club's official website. "They are ready for those steps and have got to be playing against men to show what they can do and push on from now. Once the window shuts, you know exactly what you've got and what your numbers are."
Man United's Under-21s side were crowned champions of the Premier League last season for the second year in succession.