Manchester United have confirmed that Leny Yoro will be out for around three months due to injury.
Yoro had been seen on crutches with his left foot in a protective boot.
The 18-year-old had featured in a friendly against Rangers shortly after joining United but now faces a lengthy wait for his competitive debut.
A statement on United's official website read: 'Manchester United defender Leny Yoro has today had a successful surgery on his foot injury.
Manchester United defender Leny Yoro will be out for around three months due to injury
'Our summer signing from Lille sustained the injury during the team’s recent friendly match against Arsenal in Los Angeles, USA.
'Yoro’s rehabilitation starts now and we look forward to the 18-year-old returning to fitness in around three months.'
United are also currently without forward Rasmus Hojlund, who has a hamstring problem.
Erik ten Hag has suggested that Jadon Sancho could start the season up front for United, with new arrival Joshua Zirkzee still working his way towards match fitness.
Asked about the possibility of starting Sancho as a striker, ten Hag said: 'That is what we can do if we don’t have the availability of Rasmus. Of course, Joshua Zirkzee is coming in.
‘He has started training. But he is not so long in training so it it will take time and he has to adjust to English football and our way of playing.
'Jadon can, of course, play as a striker. He can also play in wide areas but it could be that he is a good option.’