Ferguson said Smalling was suffering from tonsillitis and will play against Newcastle next Wednesday or Manchester City the following Sunday.
"I have seen the reports," Ferguson said. "They are well wide of the mark. He has tonsillitis."
Ferguson also revealed that he could have Rio Ferdinand and Phil Jones available for Saturday's clash against Blackburn at Old Trafford.
There were claims on Friday that Smalling, 22, could be out for up to three months which would have added to United's injury woes.
Looking further ahead, Ferguson said he sees Tottenham as one of the main challengers this season for the Premier League title.
"They are playing the best football in the country," he said. "They could win it on this form."
And the United manager, who celebrates his 70th birthday on Saturday, said the club will look at exercising their option on Dimitar Berbatov's contract in March.
The Bulgarian has just six months left on his current deal, but there is a clause which means United can offer an extra year.