Owen Hargreaves may not play at all on United's pre-season tour of Asia due to injury.
The 26-year-old midfielder, who signed earlier this month from Bayern Munich, has travelled with the squad to the Far East but missed the first match against Urawa Red Diamonds in Tokyo on Monday.
It could be a frustrating wait for the England international, who spent a year holding onto the hope that his transfer to Old Trafford from Bayern Munich would be completed.
Hargreaves is suffering from tendonitis in his knee, an injury that is not considered serious but enough to jeopardise his involvement in the remaining Asia Tour games against FC Seoul on Friday - where fellow new signing Nani could make his debut - and next week's clashes against Shenzhen FC and Guangzhou Pharmaceutical.
"Once we get home, we have half a dozen games to play before the season starts," Sir Alex told PA Sport.
"Ideally, I would like everyone on tour to have got at least two games under their belt by the time we get back.
"But with the ones who are injured (Hargreaves, Darron Gibson and Lee Martin) we have to make an assessment about how they are progressing and they may have to wait until we get home."