Anelka (groin) and Sinclair (hamstring) could both return to the squad to face Villa.
Clarke said: "Scott has been in and out of the group but training with us.
"He just needs careful management with his injury to make sure he comes back 100 per cent ready to go.
"We knew at the time when he did it that it was a significant hamstring injury.
"It's seven weeks since Manchester United now and hamstrings can take anything between three and eight weeks.
"It's frustrating but he knows it is part and parcel of being a footballer.
"He's done his rehab well and he's back in the group now and building up the day-to-day fitness that will mean he's ready to go when we ask him to go."
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