DEFENCE wins premierships. That much we know.

Only twice (Hawthorn in 2012 and '13) in the past decade has a team won the flag without ranking top four in the AFL for fewest points against.

But how do you rate a backline? Should you only consider the qualities of each team's back six?

West Coast's undersized defence was outstanding in trying circumstances last season, but they couldn't have done it without pressure applied further up the ground.

And these days defenders do much more than simply defend.

The Western Bulldogs took a leap forward last year, partly by locking down opponents, but also by attacking in waves from half-back. So where should they rank?

These are just some of the questions AFL.com.au reporters considered when putting together a ladder rating each team's defence.

Fremantle's whole-team system was thought to be the League's best, with Ross Lyon having perfected the art of a shutdown.

Hawthorn – the AFL's tightest backline last season – came in second. Scoring against the Hawks is possible, but you’ve got to get the ball off them first.

Most of the better teams feature higher up in our rankings, although we've tried to predict how their defences might perform with new personnel and some off-season tinkering.

We're backing in the Swans, still optimistic about the Eagles despite their Grand Final woes and predicting more tough times for a couple of last season's cellar-dwellars.

1. Fremantle

They're not known as the most defensive side in the competition for nothing. Ross Lyon's game plan has seen the Dockers ranked among the top four teams in the competition in four defensive categories in 2015. They're strong in restricting the opposition from holding onto the ball when in attack, third when it comes to having goals kicked against them from inside 50 entries, and overall, were narrowly second behind the premiers in points scored against.

2. Hawthorn

A healthy balance between attack and defence has helped the Hawks to their three-peat. As well as scoring the most points this season, they conceded the least and were in the top four when it came to their defenders putting on pressure per each disposal of the opposition's forwards. Backmen Josh Gibson, Ben Stratton, (now-retired) Brian Lake and James Frawley – plus ruckman Ben McEvoy – made up their top five when looking at one percenters.

3. Sydney Swans

The Swans have been known for their stinginess in recent years and were ranked fifth this season for points scored against. They were clear leaders when it came to applying pressure to their opposition's forwards and were also best at ensuring the other team struggled to take marks inside their forward 50. Their opponents also only goaled 20.9 per cent of the time they took the ball inside 50; again, the Swans were the best in the League in that area but fell down when it came to winning defensive one-on-one contests, where they were ranked in the bottom four.

4. Richmond

The Tigers might not have won a final for a third-straight year but their defence held up well, with this year's club best and fairest winner and two-time All Australian Alex Rance leading from the front. They were third overall for points scored against and were particularly good at restricting the opposition from retaining the ball when they took it into attack. They were also in the top four for groundball get differential, showing they defended well at the coalface when required.

5. West Coast

The Eagles were forced to rethink their entire defensive approach early on after losing key posts Eric McKenzie and Mitch Brown to season-ending knee injuries, but it wasn't the disaster many predicted with their full field "web" strangling the run of opponents. They were the fourth hardest team to score against, and while they were ranked in the bottom four when it came to pressure specifically in defence, they were third best at restricting their opponents from taking marks inside 50.

6. Geelong

Harry Taylor's influence on the Cats is born out in the statistics, with Geelong's defence the best at intercepting opposition teams' forward 50 entries. They also use the ball well out of the backline, rated among the top-four in the competition. The Cats were ranked eighth in the League for points against last year but should be a tougher team to beat in 2016.

7. Adelaide

Adelaide has an understated and unheralded backline that is superbly led by 2014 best and fairest winner Daniel Talia. Last year the Crows were difficult to overcome: they were ranked sixth in the competition for points conceded. They are steady in most key defensive areas, showing an evenness in their approach and set-up.

8. Greater Western Sydney

Injuries to some key defenders hurt the Giants last season, but their backline structures still held up well. The Giants averaged 6.9 intercept marks a game (third best in the AFL), and were also top-four for limiting the opposition's goal scoring per inside-50 entry. The Giants' opponents kicked a goal 23.9 per cent of the time they went into their forward 50.

9. Essendon

Essendon's poor 2015 season saw them concede some big scores, which pushed them down the order for points against. But they have Michael Hurley and Cale Hooker, both All Australian defenders over the past two years, and ranked second best in the competition for defensive 50 inside marks last season. They also defended well at ground level, recording the second highest groundball get differential.

10. Collingwood

If intercept marking is seen as the key statistic in the back half, Collingwood falls down in this area. The Magpies took just 4.4 intercept grabs a game last year – the lowest of any club. The Pies are solid in other areas and are second best in the League for winning or neutralising defensive 50 one-on-one contests.

11. Port Adelaide

On paper, the Power's best defensive line-up looks more than handy. However, injuries to key defenders Alipate Carlile and Jackson Trengove took a toll last season as Ken Hinkley's side started to leak more points. Port's backline depth is largely unproven, so they will be hoping for an injury-free run to help them climb back up the ladder. Areas requiring immediate improvement include ground ball gets inside defensive 50 (equal 2nd worst in the League) and defensive 50 kick rating (4th worst) – which Hamish Hartlett's move to half-back tried to address last season.

12. North Melbourne

Defending better must be a priority for the Kangaroos. North's backline is solid but not spectacular, however a repeat preliminary finalist should have ranked higher than the 7th-leakiest defence last season. One area Brad Scott's men were rated highly was ground ball differential inside defensive 50. But they were average in other important facets, such as intercept marking, pressure differential and opponents' goals scored once inside 50. By tightening up slightly across the board, the Kangas could take the next step.

13. Melbourne

Paul Roos' first job at Melbourne was to stem the bleeding which, after two seasons, he has done. Last year, the Dees were elite at defending one-on-one contests, winning ground-balls and taking intercept marks – three key statistics to building a successful side. The challenge is to keep improving. Melbourne still ranked bottom six for points against, but as the Demons sharpen their attack and start to control matches better, that should change. Watching Melbourne's players handle the transition towards a more attacking brand of football in 2016 will be fascinating.

14. Western Bulldogs

Former Hawthorn backline coach Luke Beveridge brought a manic playing style to the Doggies last season and it worked wonders. Defensively, they climbed from the fourth worst side in terms of points against to the seventh best. Moving Bob Murphy and Matthew Boyd to the back half made major improvements to distribution (fourth-best defensive 50 kick rating). But there's still room to improve. Beveridge's key defenders were inexperienced with Jordan Roughead moving up the ground and they conceded marks inside 50 too often (third most in the AFL). With glass half-full optimism, it means there's scope for significant improvement in 2016.

15. St Kilda

Slowly but surely, Alan Richardson's team is coming together and this includes the defence. Likes most young teams, the Saints leaked goals in 2015, but now have a good structure to stem the tide. Jake Carlisle's addition at centre half-back should help immeasurably, while Hugh Goddard shows enormous promise to shore up the key posts. The Saints were ranked in the AFL's top five for intercept marks in their back 50 and only need to tighten up a fraction to jump up the defensive ladder.

16. Gold Coast

Injuries smashed the Suns in 2015 as they were ranked in the bottom four for both marks conceded and opposition goals allowed per forward 50 entry. A fit Rory Thompson to stand alongside Steven May gives them two pillars to build around. Nick Malceski was hampered by a knee problem and needs to improve, while Adam Saad and Kade Kolodjashnij provide the polish. If the Suns can find a third tall defender – possibly Henry Schade – the back six looks settled.

17. Carlton

The Blues have started a long rebuild under new coach Brendon Bolton, starting with No.1 draft pick and key defender Jacob Weitering. Carlton conceded the most marks (14.6) per game in their defensive 50 last season, but with Weitering to team up alongside Michael Jamison and Sam Rowe, Bolton would hope this area improves. Zach Tuohy and Sam Docherty add the dash and round out what now looks a balanced back half.

18. Brisbane Lions

Aside from veteran Daniel Merrett, coach Justin Leppitsch has looked long-term and backed a terribly young defensive unit for the Lions. They leaked the most goals per opposition forward 50 entry in 2015 and conceded the second most number of marks. With more games into defence-first stoppers like Darcy Gardiner and Justin Clarke, along with young aerial specialist Harris Andrews, these numbers should improve in 2016.