The United striker is suffering from a recurring shin injury, reportedly an impact injury rather than shin splints which is a problem originally flared up following a collision with Liverpool defender Ibrahima Konate in May 2026.
Reports state United reportedly want to avoid surgery, hoping an extended period of rest will allow him to recover fully.
This period of rest will keep him out until January 2027 at the earliest, leaving the Red Devils with limited options in attack in an already underwhelming United attack.
Sesko has scored two goals in six appearances this season and manager Michael Carrick will be hoping to rotate his side before this weekend's challenge against Chelsea.
Carrick's job is hanging by a thread and whilst Joshua Zirkzee, Bryan Mbeumo and Matheus Cunha could step up, it is Marcus Rashford that many are hoping can fill Sesko's boots.
Rashford finished with eight goals and seven assists in La Liga last season whilst on loan for Barcelona as he helped the Spanish side lift the league title.
In eight appearances this season, Rashford has zero goal contributions. Sesko's injury could be key to helping him get back to his old self and back on the scoresheet for Carrick.
Rashford offers pace, direct running and the ability to threaten space behind defenders that United are severly missing. However, he is naturally more comfortable starting from the left, which may open up a route for Zirkzee and Cunha up front.
Carrick is on the brink of being relieved of his duties following a run of seven games without a win. A loss to Chelsea could mean the end for him if he cannot find a Sesko replacement as soon as possible.