The Aussie midfielder saw plenty of action last term.
Warnock told Villa's website: "I've been impressed with Herdy, especially when you consider that he wasn't really seen as a central midfielder.
"It's not easy because at full-back you haven't got players behind you trying to nick the ball off you. Everything is in front of you. When on the ball in central midfield, you've always got people rushing to tackle you left, right and centre and you get pressure from every angle.
"There's a lot of pressure in central midfield because you've got to be able to keep the ball, win it back, be the all-round player really. There's a lot of pressure in there but he's done it really well.
"Chris is a great player. He is comfortable on the ball. He wins it back really well. He's looked comfortable doing his job.
"The challenge now is to consistently do it over a season. That's the big ask. A lot of players come into the team and do it for several games. It's carrying it on for the season."