The Swede was forced off before halftime of last night's Carabao Cup quarterfinal defeat at Tottenham.
Amorim told MUTV: “I think he has something we have to assess to say specifically what he has but it’s tough to lose a player.
“They work really hard, they want to return but like I said, the same thing with Luke Shaw, Mason Mount and Vic, they had injuries, they don’t have space to train.
“Just preparing games is not perfect so we’ll try to do it again altogether to have the full squad because with this schedule we need the full squad.”
Last night marked Lindelof's fifth start for United in an injury-plagued season.
- Get breaking football news faster with the new Tribal Football app! Download now on iOS and Android to stay ahead of all the latest transfers and football updates. Download now: App Store, Google Play