The Swedish central defender struggled during in last weekend's shock home defeat to Crystal Palace and was then left out of United's victory over Luton in the Carabao Cup.
He returned on Sunday for the thrilling win over Brighton but there are serious concerns inside Old Trafford that Lindelof is struggling with fatigue after an exhausting extended 2019-20 campaign.
Lindelof, 26, made 47 appearances for United last season but was left out of his country's UEFA Nations League clash with Portugal last month with the Swedish medical team worried by his physical condition, says the Mirror.
All parties are set to discuss the matter in the coming weeks.
The Swedes are scheduled to play three games in six days, with a friendly in Russia before Uefa Nations League clashes away to Croatia and Portugal.