Ferguson: Rooney injury not serious
United, facing title rivals Chelsea on Saturday in the Premier League, slumped to a 2-1 defeat by Bayern Munich in the Champions League quarter-final first leg with Rooney injuring his ankle in the final minutes.
"He hurt his ankle and we will know better tomorrow," Ferguson told reporters.
"I don't think it is terribly serious but we will wait and see."
Asked whether his participation against Chelsea was in doubt, Ferguson said: "I can't answer that. We have to see tomorrow."
Rooney gave United the lead in the second minute with a close-range volley but the visitors conceded two second-half goals including a stoppage-time winner from Ivica Olic to hand them their first away defeat in the Champions League this season.
The England striker has been in top form this season, netting 34 times.