Williams, 24, has been out of action since October when he aggravated a foot injury while playing for Wales in their World Cup defeat to Australia.
That meant a second operation for Williams who is now scheduled for a return to action in the coming weeks.
But Pivac insists that they will make sure Williams is 100 per cent before bringing him back with the Six Nations looming large in February.
"He is still a few weeks away," he said. "Yes, it is good to see him out of the boot and up and starting a running programme, we have just got to make sure we get it right and don't expose him too early.
"We are obviously aware there is a Six Nations around the corner and we are doing everything we can to get him right so he can play for us and play for Wales.
"It is just one of those things, week by week he has got to pass certain stages. The reality is he needs to get every week under his belt and then he moves on to the next week.
"There is no real finish line, we don't want to put that pressure on him. Considering he has had the two surgeries on the foot we have got to be very careful.
"There are 101 reasons to get him 100 per cent right, which is what we are going to do. We are not going to be putting him out there any earlier than he has to. We will be looking after him."
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