WEST Coast's reigning best and fairest Eric Mackenzie is back running after his knee reconstruction and expects to be in full training at the start of pre-season in December. 

Mackenzie ruptured the anterior cruciate ligament in his right knee in the Eagles' first NAB Challenge match of the year against Carlton on February 27.

The 27-year-old had a traditional knee reconstruction and has been diligently working through his rehabilitation in order to be ready for the start of pre-season training.

On Monday morning, Mackenzie ran for the first time since his surgery and he told the Eagles' website that he was on track to be ready for full training in December.

"It's pretty good to be back running," Mackenzie said.

"It was probably one of the worst runs I've ever done, but it felt good.

"It's now about getting the confidence back. I've been able to build the strength in the gym, so I've got that. I know it's going to be strong enough. It's just a matter of trusting it again.

"Getting through that first session, it's a huge tick, a big milestone. That's what this whole year is about, just reaching each milestone as it comes.

"Day one pre-season I should be in the majority of training … I should be good to go from about December." 

There were grave fears for the Eagles this season after both Mackenzie and fellow key defender Mitch Brown suffered season-ending knee injuries.

Brown, who suffered the second ACL injury of his career in round one against the Western Bulldogs, also had a traditional knee reconstruction.

But the backline has functioned magnificently in their absence - the Eagles have the third-best defence in the competition and opposition coaches have lauded their structures behind the ball. They are also the League's No.1 intercept marking team, with youngster Jeremy McGovern leading the way.

Mackenzie said he might find it hard to regain his place in the side given the team's form so far this year. 

"The boys are flying," he said. 

"I'm going to struggle to get my spot back I think the way they're going. 

"They've gelled very nicely playing such a good system." 

Mackenzie did his running alongside veteran Sam Butler, who is nursing a hip problem. Butler was selected to play against Adelaide last Saturday night but was withdrawn late on Friday due to the soreness.

He ran more laps during the Eagles' recovery session on Monday afternoon but will have a race against time to be fit for Saturday's crucial clash with Collingwood at Etihad Stadium.