It's a transition made easier by the addition of smart teammates such as fellow midcourters Peta Toeava and Tayla Earle, who O'Brien has traded bibs with throughout the season.
O'Brien credits their team culture as a huge part of the Mystics' consistently successful performances that helped them to clinch their first premiership title last year, and they look well on their way to claiming another in 2022, sitting atop the table after 11 games.
"I feel like we're constantly growing and offering what we can to each other which is helping grow us as a team.
"Just the nature of our team, we're quite supportive. We are all pushing each other at training and having that experience around you as well is only helping your teammates."
And for O'Brien, a specialised wing attack, pulling on the centre bib in the ANZ Premiership is all part of the learning experience.
"I'm not very familiar with the centre position, so I've still got a lot of work there in that position but I am enjoying it, it's a different feel.
"It's something I can keep improving on and I'm able to develop in that area as well so it's been a cool opportunity to grow that part of my game."
It's an opportunity she's grabbing with both hands, after suffering an Achilles rupture in 2018. After not expecting to get a great deal of court time last year for the Mystics - let alone in the grand final - O'Brien has already played in all but one of the Mystics' games this season and looks on track to double the number of minutes played last season.
"I feel like when you're playing you get to practise the things that you've been doing at training so it's cool. I'm relishing the opportunities and it's been lots of fun as well with the group that we have."