ROBBIE Tarrant has quietly become one of North Melbourne's most valuable players over the past 18 months.

As recently as round two last season Tarrant could not make North's best 22, overlooked for the Roos' opening two games of 2015 as Joel Tippett was preferred in defence.

At the time, Tarrant was coming off two injury-riddled seasons, when on-going tibia problems had restricted him to 14 games, including just one in 2014.

He was also embarking on a career change. Having spent the previous three seasons in attack, Tarrant had been reprogrammed over the 2015 pre-season to play as a key defender.

The former Bendigo Pioneer started his AFL career in defence but it seemed a temporary measure at the time given he had been recruited as a key forward.

Since earning a recall in round three last season, however, Tarrant's form in defence suggests he has finally found his football calling.

And Champion Data statistics show the attacking instincts he honed as a forward have been a significant factor in his rise as a backman.

After North's club-record 9-0 start to 2016, Tarrant is ranked elite for a key defender in kicks (10.7 a game), metres gained (276 metres) and uncontested possessions (10.9).

Tarrant has shown an increased willingness to fly for marks inside North's defensive 50 this year and more often than not clunks them.

His above average rating for intercept marks (2.1 a game) illustrates how he has helped cover the absence of Lachie Hansen from North's defence for all bar one game this year.

Brad Scott is all smiles with his in-form defender Robbie Tarrant. Picture: AFL Media

Tarrant's defensive stats stack up well too.

He is the only key defender in the competition this year rated elite for metres gained and above average for spoils (seven a game).

He has been out-marked in just two of the 20 one-on-one contests he has defended, and subsequently lost another two of those contests through a free kick or his opponent winning the ball at ground level. This puts him equal sixth with West Coast's Eric Mackenzie among the 33 key backmen who have defended at least 20 one-on-one contests.

Tarrant's speed off the mark is reflected in his ranking of equal ninth among the AFL's top-30 defenders for spoiling his opponent on the lead.

Tarrant's stats read even more impressively when you consider his opponents this season have included Taylor Walker, Jesse Hogan and Nick Riewoldt.

On Friday night, Tarrant is likely to spend at least some time on rejuvenated Sydney Swans superstar Lance Franklin, especially when the five-time All Australian plays deep inside the Swans' forward 50.

Franklin's freakish mix of speed, endurance, strength and cat-like agility at ground-level makes it almost impossible for one opponent to stop him.

But Tarrant is as qualified as most key defenders to take on the assignment.