"Yak's been out for nine months and he will have to get a lot of training and a lot of football under his belt before we feel he's ready to start Premier League matches again," Moyes told evertonTV.
"He played 45 minutes for the reserves again this week but felt his hip and his back tighten up so we had to take him off."
The Nigerian ruptured his Achilles in November last year and following an operation he has been gradually building up his fitness, culminating with a first appearance for the reserves last week.
He scored after just 30 seconds but Moyes is urging caution.
"We have to understand that he has been out for a long time," he added.