The pair will take centre stage in the biggest match of the year for the two New Zealand franchises. The winner will move on to the preliminary final and a match-up with either the Thunderbirds in Adelaide or the Swifts in Sydney, while the loser gets to spend the next 12 months reflecting on what might have been.
So there is a lot at stake, and the ever-smiling, always upbeat South African-born duo will be at the forefront of a fascinating battle which pits structure against instinct, precision against flair and teamwork against individual talent.
The Steel has stood out for its methodical execution of coach Robyn Broughton's game plan. The combined Otago-Southland team is not without its stars but, as a whole, it is greater than the sum of its individual parts.
The Waikato-Bay of Plenty Magic, on the other hand, has been solid one moment, flaky the next. Brilliance from the likes of van Dyk, defender Casey Williams and centre Laura Langman has helped dig the team out of some holes.
It is a clash of styles, and honours are even this season. The Magic won 47-41 in round two and the Steel exacted revenge in Invercargill last month.
The de Bruin-van Dyk skirmishes were intriguing and promise to be a highlight again.
"It is not the easiest when you are playing against your best mate," de Bruin said.
"We do have the odd Afrikaans conversation but the semifinals are business time. If you lose, you're out, so I don't think there'll be a hell of a lot of love to share."
De Bruin moved south from the Magic to link up with the Steel this season and has been a dominant force at the back. All the talk pre-season was whether the former Silver Ferns defender would regain her touch after having her first child, Caleb, late last year.
But motherhood seems to agree with the 1.9m goal keep. She is fitter than before giving birth and her form should see the 32-year-old return to the national team.
"It definitely feels like it," she responded when asked if she is fitter.
"Just mentally you can push yourself so much harder after giving birth. I'm a lot busier than I used to be and you have to value the time that you have in the gym."
As far as her form goes, de Bruin said she was responding to the challenge of having some younger players around her.
"There is always areas to work on but I'm enjoying myself at the moment. I enjoy the responsibility of being the leader and the old head at the back ... I thrive under that sort of pressure."
With the retirement of Megan Hutton and the season-ending injury to Sheryl Scanlan, defence shaped as an Achilles heel.
But de Bruin's combination with former shooter Te Huinga Reo Selby-Rickit has instead got the Steel on the front foot.
The pair combined beautifully to help restrict van Dyk's supply of ball in the five-goal win in round 10.
The teams have plotted different trajectories in reaching the playoffs. The Magic's hopes threatened to unravel with three consecutive losses. It then stumbled to an unconvincing win against the Central Pulse but rediscovered its best against the Adelaide Thunderbirds, winning 53-44.
The Steel made a slow start to its campaign, but won four games in a row to keep its hopes alive before coming unstuck against a determined Swifts team in Sydney on Monday night.
The 55-38 defeat left a dent in the team's morale.
"They [Magic] had one of their best performances last week and will take a lot of heart from that. But I think the biggest lesson we learnt against the Swifts is that we can't afford to drift from our game plan," de Bruin said.
"We have to keep our concentration for the whole 60 minutes ... Otherwise it will end like it did on Monday night."
