Mullett pondered this question after narrowly missing selection in last year's elimination final against West Coast.
To a large extent, Mullett already knew the answer.
Ever since he joined North in 2010 via the rookie draft, the half-back had been told the same thing by Roos coach Brad Scott and his assistants: "You get the ball enough, you just have to defend, defend and defend."
That advice really hit home after Mullett watched the Eagles pummel North by 96 points last September.
He carried it with him into the 2013 pre-season and the hard work he put in then has helped him make an outstanding start to this season.
After playing just nine games in his first two years at North, Mullett has not missed a game in 2013 and has formed a damaging partnership with fellow half-back Shaun Atley.
Mullett, 21, has a licence to attack most weeks and he has used it liberally in the first 10 rounds.
The classy left-footer is averaging 20 disposals a game to be the fifth highest possession winner at North in 2013. He is also ranked second at North and equal 19th in the competition for rebound 50s (35), fourth at North and equal 17th in the AFL for bounces (15), and has kicked five goals.
Mullett was nominated for the NAB AFL Rising Star award after racking up 21 possessions and kicking a goal against Geelong in round two.
In North's 68-point win over St Kilda last Sunday, he had a career-high 31 possessions and kicked a goal.
But Mullett says none of this would have been possible if he had not committed to his new mantra – defend first.
"It's a massive achievement for me to play the first 10 games because I didn't know where I was sitting coming into round one," Mullett said.
"My focus going into the pre-season was defend first. I was told if you defend well you'll get a game so that was my priority coming into the pre-season.
"The main focus with all of my clips is if I defend well I get the ball. If I defend and get a spoil in I usually get on the end of it, but if I drift away from that I usually don't get the ball.
"More importantly, if you don't defend you get goals kicked on you and you lose the game. So what I'm learning now is to defend as if your life depends on it."
Mullett said it was largely pointless racking up possessions across half-back if you don't keep your opponent in check.
But Mullett's improved defensive efforts have ensured he's been able to do both.
Against the Saints, he kept star small forward Stephen Milne to one goal, out-bodying him in several one-on-one contests and taking two contested marks.
Mullett also held explosive Western Bulldog Luke Dahlhaus to one goal in round seven.
Mullett said he got more satisfaction from restricting the influence of such important opposition players than he did going on a long run from half-back.
"If Milne had kicked a few on me and I still got 30 (possessions) I wouldn't be happywith my game at all because I'd have let the team down by letting Milne get off the leash," Mullett said.
"So the way I go about it is focusing on my defensive efforts because I know that's what the coaches rate me on."
"I've been doing a lot of work with our defenders like 'Spud' (Michael Firrito) and 'Scooter' (Scott Thompson) on one-on-one contests because they just know how to use their bodies well.
"I'm feeling a lot more comfortable now that if I get dragged one out in the goal square I can beat my man."
Mullett says a defensive mindset will also be vital as North attempts to resurrect its season after a disappointing 4-6 start.
The Roos have had no problem scoring in 2013, averaging the third highest score per game, 109.7 points.
But they are ranked 14th for points against, conceding 96.7 points a game, and too often have been unable to stop opposition run-ons.
"Restricting teams is going to be a massive focus for us, especially at the end of the year," Mullett says.
"It's going to determine whether we make the finals ornot because we know we can score quickly and efficiently.
"But if we just defend, defend to get the ball back, we're going to be a far more consistent team."
