All Australian defender Michael Johnson has turned his back on free agency to sign a two-year contract extension with Fremantle.

Johnson was set to become an unrestricted free agent at the end of the 2015 season, but has now committed to Fremantle until the end of 2017.

The 30-year-old admitted on Tuesday that a number of clubs had contacted his management, but he said he never considered leaving Fremantle.

Johnson repays the faith

"There were a few clubs that approached my manager," Johnson said.

"I was an unrestricted free agent at the end of the year so there were a few clubs that put their hand up. But I knew my manager was working really closely with Fremantle Football club and we knew there was going to be a deal done soon.

"I'm stoked, the club's stoked and all my family is really happy as well."

Johnson has become one Freo’s most valuable players in recent years and was named All Australian in 2013 when the Dockers played in their first ever Grand Final.

He said the prospect of being a Freo Docker for life is something very special to him.

"I think it's a big thing for all AFL players," Johnson said.

"To last over 10 years and be a one-club player, it's something special.

"When I leave the club after a few more years I'll look back and just see the way the club has developed me as a player and as a person, and I can look back at it as a big part of my life. So hopefully I finish my career here."

The 193-game veteran suffered a serious back injury late last year that ruled him out of the finals series and hindered his pre-season significantly.  Johnson revealed that he did wonder about the long-term impact the injury may have on his career.

"It did go through my head," Johnson said.

"But I had faith in the medical staff and specialists that we saw away from the club.

"I ticked every box after the surgery and I was well ahead of schedule. It's been really good to get out there and play with the boys in the NAB Challenge and the scratch matches and I've slowly built from there and I'm feeling really good at the moment.

"I'm nice and strong and moving well on the ground. It hasn't slowed me down at all and I think I'm playing really good footy at the moment."

Johnson said he stills feels young of mind despite his body getting a little bit older.

He said the performances of the Freo Dockers' younger brigade is motivating the older players to perform week after week.

"You look at the young guys that are coming through the ranks and you draw strength from these young guys that are performing well on the training track, over pre-season and on game day," Johnson said.

"I'm getting old, but I love running out there with the young guys because they help you find more strength on game day."