Precautionary fitness concerns saw Fellaini sit out Belgium's 1-1 draw against the Netherlands in an international friendly on Tuesday, but coach Roberto Martinez suggested there was likely to be little problem in being ready for club action a few days later.
"He should be fine, it's just he wasn't 100%," the Spaniard explained.
"He's got an important game at the weekend and this wasn't the game to use players who weren't 100%. We expect he should be fine in the next couple of days."
It is alleged that while the 30-year-old felt 'slightly under the weather' after returning from international duty, it was he who had insisted that he take part in the session, only to hobble away towards the end after seemingly suffering an ankle problem.
Crucially, Fellaini apparently needed no help from staff or colleagues in returning to the changing rooms and fans will therefore hope that The Sun's claims and attention grabbing headline have been exaggerated and that the problem is only minor.
Fellaini, who has struggled with niggling injuries throughout his United career, has excelled in a deep lying midfield role so far this season. United have won every Premier League game that he has started, while he was brought on at half-time when the team was trailing against Newcastle.