McFadden is making good progress from the setback suffered in training in early September.
McLeish believes the Scotland international is benefiting from being in prime physical condition.
But he knows the dangers of recalling the ex-Everton player ahead of schedule however encouraging the medical bulletins may be.
McLeish said: "The progress Faddy has made, you are thinking 'wow, he's going to be back quick, back before Christmas'.
"But you have to be careful and put the reins on a wee bit and let things heal properly.
"The actual rejoining of the cruciate actually has to take time to heal."