Van Dijk has been out of action since October when he picked up a serious knee injury and had to undergo surgery to fix the damaged anterior cruciate ligament.
The Dutchman has been undergoing his rehabilitation process away from England, in Dubai, and there is real hope that he could be back in action before the end of the season.
However, former players have warned that the defender should not look to rush back after such a serious injury and Warnock feels it could be a while before he can play at his previous levels.
Warnock also suffered a similar injury and he also cited the example of Aymeric Laporte, who is now finding it hard to get into the starting eleven for Manchester City.
He warned Liverpool that from the date of his return, it could be another year before Van Dijk can get back to playing at his best again.
The former Red told The Athletic: “It took me a long time to come back.
“You only have to look at Aymeric Laporte at Manchester City to see that he’s not come back in and taken his place in the backline.
“He’s finding it very difficult to find his form at the moment.
“I might be completely wrong but I am just thinking of it from what I have been through and what I have seen from other players.
“I don’t think you will see the best of him for 18 months.
“When I say 18 months I mean from point of injury to returning to the first team.
“He might come back after nine months, eight months but then it might be another year before you might see the best of him.”
Liverpool have acutely missed their defensive leader and his absence saw them drop out of the title race by January.
