Ferguson took a risk fielding Ferdinand against Roma last night - only three days after the centre-half limped away from Middlesbrough with his left foot in a surgical boot.
At Old Trafford, Ferdinand required three stitches in a gash to his right foot, rather than the bruised left one, at half-time.
"Rio should be fine for Arsenal. His foot was OK, it was only bruising - and he cut the other one," said Ferguson.
Mikael Silvestre at left-back played his first game since sustaining a cruciate knee ligament injury in September, and Gary Neville also made a comeback from long-term injury as a late substitute.
"It was very good to have Gary Neville and Silvestre back," said Ferguson. "It just gives us a little bit of experience."