With a game-high 14 intercept possessions, six spoils and three contested marks, Tim O'Brien's effort in the Hawks' recent upset win against the Bulldogs landed him a career-best performance.

The 27-year-old dominated in defence - an area of the ground where he has only just found his feet in recent weeks.

The 193cm target has been a fixture in the forward line for most of his time, but a recent shift down back is beginning to prove a favourable switch.

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Speaking post-game following Saturday's victory, O'Brien said he has enjoyed the move playing the back six.

"It's just a bit of belief that I can play in the backline, I've played there now a couple of weeks in a row," he said.

"I've got to understand the system, and then it's just playing at my strengths, not worrying about anything else and just going for the footy.

"I've been working on a lot of things in the background so it's good to see them come out in the game."

Having previously shared his time between forward and ruck duties, O’Brien played an important role for the Hawks last year as long-time sole ruckman Ben McEvoy transitioned to a role as a key defender.

Now having played in defence during the later end of the season himself, O'Brien has averaged 6.2 intercept possessions, three spoils and 2.2 contested grabs across the last four rounds.

Hawthorn initially selected O'Brien with Pick 28 in the 2012 AFL National Draft, before he spent 2013 developing in the VFL with Box Hill, where he played in their premiership winning side.

Hear more from O'Brien following Saturday's victory.