THE RETIREMENTS of Tom Lonergan and Andrew Mackie have left a gaping hole in Geelong's backline, but the departures of two club greats has opened the door for a number of emerging players to step up and make a position their own.

That is the view of defensive coach Matthew Scarlett who has nominated Jake Kolodjashnij to take a giant leap forward in 2018 following a stellar pre-season.

Scarlett said the continuity and confidence Kolodjashnij had gleaned over the summer would have him in a good position to take the role Mackie played across half-back and on the wing.

"Kolodjashnij is the one for mine," Scarlett told AFL.com.au.

"He didn't do much in pre-season last year, he had his groins and glandular fever.

"He hasn't missed a session this year. So hopefully he can have a big year, whether that's around the footy or down back he's going to be pretty versatile."

Kolodjashnij succumbed to a groin injury late last pre-season and that, coupled with a bout of glandular fever, saw the 193cm and 94kg defender miss the first seven games of the season.

The 22-year-old gradually built his confidence in the VFL and returned to the senior team against Essendon in round eight.

With Harry Taylor heading to the forward line, Kolodjashnij started his 2017 campaign as the club's third tall defender alongside Lonergan and Lachie Henderson.

However, the Cats' match committee decided to trial him on a wing in the second half of the season and the positional shift saw his output increase.

From 18 games, Kolodjashnij averaged career highs in disposals (14.6), marks (4.4), inside 50s (2.4), rebound 50s (1.5) and uncontested possessions (10.8).

After speculation over his future, Kolodjashnij re-signed with the Cats until the end of the 2019 season – emphasising the confidence the club has in him becoming a reliable long-term player for the club.

If his body remains sound, he will bring up his 50-game milestone in round three against West Coast at Optus Stadium in Perth.

The Cats' coaching staff have planned for Taylor to return to defence in 2018, while Henderson has had an interrupted pre-season after undergoing surgery on his knees twice.

"It's going to be a bit slow for 'Hendo' but hopefully he'll be out running in the next couple of weeks. He might be one that starts the season a little bit slowly," Scarlett said.

Cameron Guthrie has been training in defence and appears likely to play down there more often in 2018, while Jed Bews, Tom Stewart and Zach Guthrie, along with Zach Tuohy, will also feature in a revamped backline.