Although just one kilogram lighter on the scales, Rockliff is noticeably trimmer at Lions training, after altering his diet and adhering to some harsh words from Voss and his coaching staff.
Rockliff, still just 22, is a vice-captain, one of the most respected players at the club, and the 2011 club champion, but after tailing off in the back half of last year, he took in some criticism.
He came to the Lions via the 2008 pre-season draft, and despite continually improving his aerobic base over the past four years, knew he still had work to do.
"I got a pretty scathing review at the end of the year from people at the club and got hit between the eyes and took it on board and moved forward," Rockliff said.
"From Vossy the most. He came at me pretty hard. Woey (midfield coach Shane Woewodin) had a few comments as well.
"It was all fair and reasonable and we worked through it and I think I've been training the best I ever have.
"I'm definitely in the best shape I ever have been and running the best I ever have."
Rockliff has hovered around the top-10 of the club's 2km time trials during the pre-season. That is a vast improvement from his early days when he battled with renowned endurance struggler Ash McGrath at the back of the pack.
Even as recently as last year, Rockliff was no better than mid-field.
He said a change of diet had enabled him to shed body fat while retaining his strength.
"Just the meal size and stuff like that," he said. "We've got some new dieticians on board this year which has been helpful with a new plan.
"That's been my downfall as a professional athlete, my eating, and I've definitely made progress on that, but still a fair way to go."
Rockliff finished sixth at the Lions' best and fairest last year but faded in the final six rounds.
One of his great strengths as a player is his ability to rest in the forward line and kick goals as a small marking forward.
He said the leaner frame would not hinder that attribute.
"I don't think I've lost any strength. I've been trying to work on my leg power and core strength so hopefully I'm stronger than what I have been in the past and weighing slightly less," he said.
"I've never been a massive lifter in the gym, but I've definitely been trying to work on my leg strength and core strength."
Rockliff said he had been impressed with the running ability of Melbourne recruit Brent Moloney, who looks right at home in every drill.
"I always thought he was an inside me that wasn't a great runner, but he's been really impressive.
"I can't wait for the games to come around. The boys have all been training well, although every club says that in the pre-season and you don't really know until you come up against opposition."
Michael Whiting covers Brisbane Lions news for AFL.com.au. Follow him on Twitter: @AFL_mikewhiting
