LEVI Casboult could look to revive his Carlton career in the backline in 2019, having been trialled in defence during a gruelling pre-season training session on Friday.

The Blues were put through a punishing session that lasted nearly three hours in sweltering heat that hovered at just over 40 degrees Celsius at Ikon Park, with Casboult used predominantly in the backline throughout the morning.

With the Blues having shifted the session forward to 8am due to temperature warnings, players completed a number of exhaustive drills and a lengthy match simulation, before being led through a series of demanding sprints to bring training to a close.

However, relief was soon forthcoming, with the entire squad completing the session with a water balloon fight orchestrated by forwards coach David Teague.

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The strong-marking Casboult spent the entirety of Carlton's full-ground match simulation as the deepest defender, handed imposing roles on Charlie Curnow and Harry McKay.

He performed admirably, taking a couple of nice intercept marks while floating away from his opponents, having lost his position in Carlton's developing forward line late last year.

Casboult, 28, has spent his entire AFL career as a forward, but was dropped multiple times last season after a difficult campaign in which he managed just 12 goals from 10 games.

The club's talented young duo Curnow and McKay, along with teenager Tom De Koning, were preferred to Casboult throughout the final month of the 2018 season.

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A number of defenders are in a lengthy Carlton rehab group –including Sam Docherty (knee), Caleb Marchbank (back), Lachie Plowman (knee) and Liam Jones (hand) – meaning a role could open for Casboult in the Blues backline this season.

Fellow young defender Tom Williamson was also restricted to running laps on Friday as he continues his recovery from a season on the sidelines with a back problem.

But according to new recruit Nic Newman, the loss of several key players to injury won't put any added pressure on a Blues back six that was tormented at times last season.

"Even if he was playing, we didn't want to have to rely on Doc to do it all," Newman said.

"For us as a backs group, whoever gets picked each week, we've all got to do it. For us, the standard at the footy club is that you've all got to talk and communicate and be those leaders and voices at the back. It's more important from the back half.

"You're expected to do it, no matter who you are."