Sydney Swans defender Harry Marsh is determined to make this year count.

Now in his third year at the club, the West Australian, who turned 21 earlier in the week, is enjoying an injury-free pre-season and is now looking to turn it into a big year in red and white.

“I worked hard last year and I think I started to play some good footy towards the end,” Marsh told SwansTV.

“I just really needed to keep building on my fitness and repeat sprints and I’ve been working pretty hard this pre-season and I don’t want to let the opportunity slip.

“It’s a big year for all of us (third year players) and a great opportunity to take that next step to senior level.”

Harry Marsh is fit and firing on the training track.

After being drafted as a midfielder, Marsh was switched to the backline for the second half of last season and is relishing the change of role.

“Towards the end of last year I got thrown down back and I’m loving it,” he said.

“I love playing everywhere but I think playing down back suits me pretty well.”

The defender in action during training on Friday morning at Lakeside Oval.

Marsh’s focus throughout pre-season has been working on his two-way running and getting the balance right between defence and offence.

Learning the craft of a rebounding defender has been made easier by the assistance of Rhyce Shaw who has become a close mentor over summer.

“He’s been awesome with me and obviously the other defenders, he’s been a great mentor for us all,” he said.

“He’s always just got time for you, you can always go up to him and have a chat to him and he gives you the feedback that you need, you might not want to hear it, but it’s definitely what you need, you listen to everything he says and take it on board.”

The 21-year-old is looking to make an impact in 2015.

Swans development manager Jared Crouch said he’s been impressed with Marsh’s fitness improvements this pre-season and has no doubt that he’s on the right track.

“Up until this stage he’s been working hard and has had a good, solid pre-season,” Crouch said.

“If he continues to improve, work hard and make the most of every training session then hopefully he can push for senior opportunities.”