Rooney, out with a broken metatarsal for the third time in three years, is desperate to make his comeback in United's game at his former club Everton on Saturday.
That would mean just a five week lay-off, the quickest return of any top player to suffer a broken metatarsal in recent years.
Professor Chris Moran, who assessed Rooney's metatarsal before the World Cup and an expert in bone and muscle injuries, told the Mail on Sunday: "Wayne is a fit, young lad very, very keen to return as he lives to play football. But players must be held back to stop themselves causing more damage. If you come back too early, there's a risk of re-fracturing and having a setback.
"Full-blooded and combative players (like Rooney) are more likely to get injured but Wayne's been very unlucky to have three."