"It is possible he could play," said Ferguson. "The physical part is pertinent, because the Premier League is competitive and tough. There is no getting round that fact.
"But given normal progress, he could be involved. It is a great option for us to have someone with a natural left foot in our team."
Ferguson likens Tosic to Nani of his current squad, with set-piece delivery akin to David Beckham, which could make him a very useful asset.
The player himself has been put into the care of 'godfather' Nemanja Vidic, who has helped his compatriot get used to life in the north-west.
"This is the most important day of my life," said Tosic. "Of course it is a lot easier having Nemanja here.
"He has been helping me tremendously on the field and off it as well. It is a completely different scenario to the one he faced, because he was completely on his own."
Tosic has kept a close eye on United's fortunes for years.
However, it is only relatively recently the idea of playing at Old Trafford came into his mind. Now it is agonisingly close, he cannot wait for that day to come.
"At the beginning I never thought me being anything to do with Manchester United was an option," he said.
"Then later on I was thinking maybe it could be a possibility.
"We all know what sort of team they are and what kind of players we are talking about. Now it is up to me to train and improve enough to get in the team as quickly as possible."