Davies insists Blackstock is making a good recovery but revealed he won't make the trip to Cardiff on Sunday.
He told the club's official website: "Dexter won't figure at the weekend but we are very pleased with the way he is coming along."
Defender James Perch is also hoping to get the green light to resume his comeback from injury after missing a friendly on Tuesday.
Perch has not played for Forest all season, having suffered a stress fracture of the shin during pre-season, but was on the bench against Crystal Palace at the weekend.
However, the 24-year-old has suffered a slight setback and missed Tuesday's friendly against Coventry as a precaution.
Davies told the club's official website: "James didn't play [on Tuesday] because he picked up a slight knock in training and after being out for so long we didn't want to take any risks with him."