From the most porous to the AFL's equivalent of Fort Knox, ahead of the bounce of the ball on Thursday night, we've ranked the league's best backlines.

We've already seen the back sixes that forwards across the competition dine out on. We've also seen the units that are making strides towards greatness. Now, we present the backlines that are primed to push for premiership success, the Crème de la crème, if you will.

RELATED: Every AFL club's backline ranked: Part I
SEE ALSO: Every AFL club's backline ranked: Part II

These are the teams with premiership-level defences, units with essentially no holes when healthy. Their key men can stop most opposing threats and their medium-small backs can prevent chaos and hit targets.

Many of these teams also benefit from a deep overall list and plenty of capable midfielders finding a role through the half-back line.

A couple of the sides may appear to suffer from a lack of star power, but the structure and organisation of the gameplan allow their role-players to utilise their strengths to the maximum; see Robbie Fox for Sydney or Jake Kolodjashnij for Geelong.

These are the elite backlines entering the 2023 AFL season, the teams ranked 6-1.

5. 5. Carlton

Carlton is one of the most attractive sides in 2023 with their top-heavy list and ideal age bracket, and while their backline fits these features accordingly, it is still littered with uncertainty.

Lewis Young proved to be a key recruit in 2022, demonstrating his ability to be a quality second key back on a high-performing team, but we now must see it again for a full season.

Mitch McGovern is yet to fill the expectation established by his hefty contract and his perpetual injury struggles have disallowed him to even try at times. Once again, there will be intrigue in his performance in the first few rounds; hopefully, his body can hold up.

The season-ending injury to Zac Williams obviously hurts the Blues and a replacement will be required from the collective run and ball-use from fellow teammates. Michael Voss appears to have landed on recent draftee Lachlan Cowan for the role.

Caleb Marchbank will again have to wait for his chance after yet another injury forced him to miss time. Again, Carlton may have to resort to Lachie Plowman to fill this hole unless a replacement is found elsewhere.

Despite all of the above, however, all of Carlton's defensive needs can be met elsewhere.

PERTH, AUSTRALIA - JUNE 30: Jacob Weitering of the Blues celebrates the win on the siren during the 2019 AFL round 15 match between the Fremantle Dockers and the Carlton Blues at Optus Stadium on June 30, 2019 in Perth, Australia. (Photo by Daniel Carson/AFL Photos via Getty Images)

Jacob Weitering is certainly capable of being a number one backman on a premiership team, the former number one draft pick has been one of the most valuable players in the competition since his move to full-back for the Blues.

His long-time teammate Sam Docherty was another player who produced a story-of-the-year contending season after recovering from cancer and returning to his best footy. His defensive 50 exits, ball-winning ability and contest tenacity have him placed as a potential starting midfield candidate come Round 1. He is one of Carlton's absolute machines in a team filled with superstars.

Adam Saad is one of the side's most notable players, with his explosive lane-changing run and peculiar 'woof' kick off the boot. Coming off his first All-Australian season, Saad should be primed to produce similar in his ninth year in the league at 28 years of age.

Rounding out the backs, Nic Newman is beginning to prove his placement on the team sheet, providing a quality defensive presence and offensive threat.

Some other potential defensive pieces include Tom De Koning and Jack Silvagni with their overhead abilities.