FREMANTLE defender Zac Dawson has been sidelined with a groin strain in the lead-up to the NAB Challenge.

Dawson has not trained with the main squad for the past two weeks after reporting soreness in his groin/adductor region after returning from the Christmas break.

The Dockers’ first NAB Challenge fixture is against Melbourne at Fremantle Oval on March 5.

However, there was some positive news for the club on Tuesday with experienced defender Michael Johnson finally returning to the track after months of rehab following back surgery last September.

The 2013 All Australian missed last year's finals series after hurting his back in round 23 against Port Adelaide.

Johnson, Ibbotson back on track

Chris Mayne, who was the club's equal leading goalkicker in 2011, has spent some time in defence during pre-season match simulation sessions as the Dockers look to cover all bases.

Veteran Luke McPharlin has trained without interruption throughout the pre-season and fellow key defender Alex Silvagni is also in good shape heading towards the NAB Challenge.

Garrick Ibbotson has also bounced back strongly following shoulder surgery during the off-season.