Although it was assumed Scholes had simply been rested after completing the full 90 minutes against Bolton at the Reebok Stadium, Ferguson has revealed the 35-year-old has instead picked up a niggling calf problem.
"You don't want to lose your best players, that goes without saying," said Ferguson.
"The problem is with one of those small injuries like Paul has got, when you are travelling and sitting on a plane, stiffness comes into it and doesn't make it any better.
"It was a big decision to leave him behind. Because it is only a little one, you are tempted to play him when it is not wise.
"He should be ready in 10 days."