The former Reds defender - now at Leeds United - has been impressed by the improvement our No.14 has made under Brendan Rodgers this season and is tipping him to continue to develop.
Warnock told LFC TV: "I remember watching when they played at Arsenal and he was the best player on the pitch by a mile - the distance he covered and he seemed to be playing in a more advanced role.
"I've played against him and trained with him and know he's a very good player.
"I think the first year he came was probably a bit daunting for him in realising what Liverpool is all about and things like that, but I think he's acquitted himself well this year and been very good.
"People forget he's still young. He's 22 and still has plenty of time to be a great player for Liverpool.
"This season has probably been another learning curve for him and hopefully he'll kick on to good things now - and with Joe Allen being injured, it gives him every opportunity to play."
Meanwhile, Warnock admits he was delighted when Liverpool swooped to sign Philippe Coutinho in January as he was a player whose development he'd personally taken an interest in over the last couple of years.
The Brazilian has since impressed with two goals and two assists in five appearances since moving from Inter Milan.
Warnock said: "I think since he's come in, he's adapted well to the game and the style Liverpool want to play.
"I remember seeing him for the first time when he was at Inter Milan and they played Tottenham. It was when Rafa [Benitez] was manager and he played for them a few times in the San Siro.
"I thought he was a very good player and kept my eye on him.
"He seems to be a player the fans like as well and they've taken to him. Scoring quite early on helped him, but he's been impressive."