ST KILDA wingman Jack Newnes is on a mission to add size to his frame between now and round one to help him compete as an inside midfielder.

Newnes, who was one of only four Saints to play every game last year, has been earmarked for a greater midfield role in 2015 after developing at half-back and on a wing.

The 21-year-old has grown from 76kg in 2012 to 82kg this summer, and he is hopeful a meticulous gym program will help him play at close to his ideal weight in his fourth season.

"The aim is to get right in the guts, and ideally I'd be at 84kg to play an inside role," Newnes told AFL.com.au.

"I'm hoping as the intra-clubs and NAB Cup games start coming on it'll be a bit easier to put weight on because you're not just sweating and running it all off.

"I've put on about 1kg (this pre-season) and hopefully I can get to the 83kg mark before round one."

Used mainly across half-back in his first two seasons, Newnes spent more time on a wing last year and lifted his possession average from 15.2 in 2013 to 19.9 last season.

He also won more contested ball (5.8 a game) and coach Alan Richardson has pushed him to compete with clearance leaders David Armitage and Jack Steven at training.

Newnes has also made significant gains outside the gym this summer, cutting 10 seconds off his personal best 2km time trial from last pre-season.

"My last PB was 6min 9sec, and hopefully I can knock a few more seconds off that before the start of the season," he said.

"I've pretty much run two PBs in my 2km time trials and I'm a lot fitter than I was last year.

"I’m feeling pretty fit at the moment, so hopefully I can use that coming into the season."

After the departure of champion Saint Lenny Hayes last year, Newnes said new midfield leaders were emerging and he was looking to Armitage and Steven for guidance.

Viewed by Hayes as a future captain of the club, Newnes has also grown as a leader this pre-season, with 20 players on the list younger than him.

"I'm trying to be a bit more vocal and lead with my actions this pre-season," he said.

"I'm only in my fourth year, but there's a lot of young blokes below me, so it's time to step up a little bit," he said.

"In terms of the leadership group, there's a lot of older guys that are in there at the moment and they're really good leaders so I'm still learning off those guys."

Jack Newnes has shaved 10 seconds off his 2km personal best. Picture: AFL Media