Johnson, who was named All Australian in 2013 after experiencing his own off-field issues in 2010, has been a mentor for Walters during his time at Fremantle.
Johnson has been pleased with the change in the classy left-footer over the past two seasons and said opposition sides should fear Walters given how well he is training.
"He's a funny one. It took him a few years to get up to the standard of an AFL player," Johnson told AFL.com.au.
"There was a lot of hard work through a lot of players that went through Fremantle. It started with Des Headland, and we worked really hard with Michael when he first got to the club and it's great to see him coming out the other end and becoming a really elite trainer and a really elite player of the game.
"I know that if I was an opposition player I would hate to play against him because he's quick, he's smart around goals [and] he's worked really hard on his burst of speed during training and games."
Walters topped Fremantle's goalkicking in 2013 with 46 goals and was named in the All Australian 40-man squad.
"It's great to see ‘Sonny’ do well," Johnson said.
"He's got a young child and another one on the way. So he's got that balance of work at the club and away from the club. He's worked really hard."
The most pleasing aspect of Walters’ transformation is the leadership he has shown to Josh Simpson, Johnson said.
From the remote town of Yalgoo, Simpson found his first year at AFL level a challenge. He debuted in round 23 against St Kilda, his only senior match for the year.
Simpson has also had to deal with family issues during this pre-season.
"Josh has got a different situation," Johnson said.
"Where Sonny lacked the professionalism with his diet and that, Josh is a young father. He and his partner have two children.
“[Josh is] working really hard to get his football on track and to see Sonny actually give him feedback and actually show him the way, where he stuffed up, and to see Josh working it out, it's good to see.
"It means you don't rely on the older indigenous players to get Josh on track. It's good to see Sonny has learned his lesson and he's giving feedback to the younger guys."
Johnson, also a father, said it was difficult for young players to deal with being a parent, a leader in their community, and a full-time AFL footballer.
"It's tough. It's very tough," Johnson said.
"Especially if you come from a remote community. You are an elder and you are labelled as a leader in your community and you're going to look after a young child and also be a full-time AFL player.
"It's tough. It's a big challenge. But if you can find the balance and work that out it will help your footy and your leadership around your community in the end.
"There are guys that failed but I think we have a good relationship with our indigenous players where we can help out whenever it's tough for them. It's good to see Josh is working really hard and we're here to support him."
