[RELATED: Jamie Macmillan profile | Training gallery]

He battled injuries for much of last year but 2015 has already started on a brighter note for Jamie Macmillan, with the North Melbourne defender signing a two-year contract extension.

Coming off a frustrating 2014 campaign, when he was restricted to just six games mainly due to a fractured fibula, Macmillan said he was surprised to be offered the new deal so early in the new year.

But in a show of faith by the Kangaroos, the 23-year-old has been locked away until at least the end of 2017.

"It all happened pretty quickly, but I'm rapt to get it done," Macmillan said.

"I was probably surprised a little bit that they offered me a new contract that early.

"I thought I'd just get in this year and play some more footy … I'm really looking forward to finally getting back out on the park and having a kick.

"To get it done now means now I can just play footy for this year."

Macmillan was among the Roos' best performers until injury struck in round three last year, with his fractured fibula taking a frustratingly extended period to heal.

Initially diagnosed as a six-to-eight week setback, the injury prevented him from returning until round 23 against Melbourne.

His season was then cut short prematurely by a hamstring injury suffered during North's semi-final triumph over Geelong.

While the 188cm backman has avoided any setbacks this pre-season and has completed every session so far, he isn't about to take his spot for granted, especially since the off-season arrivals of Jarrad Waite and Shaun Higgins.

"The pressure is on for spots and we know that," Macmillan said.

"So everyone's putting their best foot forward (at training) and every contest counts.

"They've settled in really well (Waite and Higgins). I've played on both of them and I think they'll be real assets to us and give us a little bit of something else up forward, which will be good and hopefully carry us one step further than we went last year."

Former Bulldogs' utility Higgins was a standout on the training track for North on Monday, racking up possessions during game simulation at Arden Street.

Waite moved well in attack and has completed most sessions since his arrival from Carlton.

Fellow big men Drew Petrie (ankle), Ben Brown (knee), Robbie Tarrant (toe) and Majak Daw (foot) trained away from the main group as they build their workloads following surgery last year.

The quartet moved well through short and sharp lateral movement drills, progressing from straight line running pre-Christmas.

Star midfielders Nick Dal Santo and Jack Ziebell also didn't take part in match simulation, but instead took part in running exercises away from the main group.