A SLIMMED down Paddy McCartin has shed weight as he prepares for 2019, new St Kilda assistant coach Brett Ratten says.

Ratten started in his new role in charge of the Saints' forward line and ball movement on Monday and saw the 22-year-old on Tuesday, as McCartin came into the club's Moorabbin base at RSEA Park.

McCartin presented in career-best shape ahead of the 2017 season but has taken that to another level, as Ratten indicated to Melbourne radio station SEN on Tuesday.

"McCartin's come back in ripping nick. He was in at the club today and he's probably dropped about six or seven kilos," Ratten said.

Injuries have plagued McCartin in his time at the Saints and he has never strung more than seven straight games together in the AFL side.

A Lisfranc sprain in his left foot ended McCartin's season prematurely, but he has since recovered from that and will be fine for day one of pre-season.

Saints football manager Simon Lethlean recently expressed similar optimism about McCartin.

"It takes a bit longer for tall forwards to reach their potential. I feel like there could be a breakout year coming for Paddy," Lethlean said.

Ratten, who arrived at St Kilda after six years at Hawthorn under Alastair Clarkson, believes he brings experience to his new side.

"I've been in the game for a long time now as a player and as a coach," Ratten said.

"As someone who's gone through a couple of clubs – I've been at Melbourne, Hawthorn and Carlton – so I've had a look at a few different environments.

"That'll be something that I'll try to add, some of those experiences that I've had."

I feel like there could be a breakout year coming for Paddy

In taking control of the club's ball movement Ratten won't copy what the Hawks did, but will take parts of their game plan.

"There will be an element of Hawthorn, but Hawthorn play like some other teams as well, so I think everyone does it fairly similar, but then there's whether the ball's in your back half or your front half, you might do it a little bit differently," Ratten said.

"Also, some of the philosophies about it – you look at some teams, they have a lot of uncontested marks, and some teams don't have as many.

"It'll be (dependent) on our capabilities as well, what we do with the footy. I'm really looking forward to that.

"There'll be a splash of Hawthorn, but it won't be about Hawthorn. It will be about what St Kilda can do."

Ratten was previously senior coach at Carlton, but said he wasn't thinking about taking up that role again if offered.

"I don't know if it will ever happen again. My focus is just to help Al (Richardson)," Ratten said.

"I've been given more responsibility at the Saints, which is what I was looking for, and really pleased to be there.

"I don't know if it will ever happen and that's something that I can't control."