Telles, 28, twisted his ankle in training at United's pre-season camp at Pennyhill Park and was absent from the matchday squad list against Queens Park Rangers.
"Unfortunately, Alex slipped and he twisted his ankle so he'll be out for a few weeks," manager Ole Gunnar Solskjaer told MUTV today.
"We hope it's not too bad."
Telles' injury could impact plans for fellow fullback Brandon Williams to head out on loan next season. Williams, 20, has generated interest from Premier League and Championship clubs.
Need a VPN? Or seeking to switch? Then support Tribal Football by clicking here to sign up with our official partners NordVPN. Not only will you receive the best VPN experience, but also great discounts by signing up via Tribal Football. Thanks for your support!