The 29-year-old captain sustained the injury when he collided with an advertising hoarding during last weekend’s game against Hull.
Rooney watched Tuesday???s match against Stoke from the stands at Old Trafford and Van Gaal explained: “It’s his knee but we have to wait to say anything about him because you never know with a knee.?? ?? ?? ?? ?? ?? ?? ?? ??
“My opinion is it’s not so serious but I’m not a doctor. We have to wait for the scan on Wednesday, then we’ll know more. I hope it’s not so serious.”
However, the Dutchman did say that Angel di Maria will miss the trip to St Mary???s next Monday.
He added: “Di Maria is not so serious but he won’t play against Southampton.???
And regarding an injury update on midfielder Daley Blind, the Reds’ supremo does not expect his fellow Dutchman to be back in action until the end of the month at the earliest.
Blind hurt his knee while on international duty and van Gaal went on: “It is not so heavy but the injury is not next week.
???Christmas maybe. I think that at the end of December maybe we see light in the tunnel.”