It was the Steel's third win in a row and once again the team was carried to victory on the back of towering shooter Jhaniele Fowler.
The Jamaican international scored from 59 of her 61 attempts and has strengthened her grip as the tournament's leading scorer.
The results have set up a couple of fascinating matches with the Magic - the first in Invercargill on Saturday and then in Rotorua on June 2.
Whoever wins those encounters can probably expect to make the playoffs.
While the Steel is improving each week, the 10-goal win against the Mystics was closer than the final score suggests. The Steel trailed for most of the game but pulled away towards the end of the third quarter.
''We've been building ... and we know Magic are not going to be easy,''' Steel captain Jodi Brown told Sky. ''They are a team full of stars but we are just growing and growing really nicely.''
Mystics coach Ruth Aitken opted to start with Bailey Mes ahead of Cathrine Latu. Latu is the most accurate shooter in the competition but getting her the ball has been a problem. That made the decision easier for Aitken, although she might have been tempted to axe Maria Tutaia, whose accuracy is well below the competition's top shooters.
The new combination started well but it was a brace of intercepts from wing defence Kayla Cullen which gave the home side an early lead.
When Mystics goal keep Jess Moulds grabbed another with three minutes remaining in the quarter, Steel coach Janine Southby had seen enough and called her troops in for a pep talk.
The sloppy mistakes just kept coming and the Steel was lucky to be trailing by just one at the break. Southby made a change with Shannon Francois replacing Courtney Tairi at wing attack.
The Mystics were still putting up more shots but the Steel stayed in touch with flawless shooting thanks mostly to Fowler.
It gets very repetitive watching the 1.98m shooter pot goals. For all that relaxed effort, though, the Mystics led 33-32 at halftime thanks to a flurry of late goals. Cullen was outstanding for the Mystics. Her timing and ability to the read the play was the main reason her side dominated possession.
The Steel had been relying on the lob into its towering shooter but had cause to reconsider during the interval.
The change came at the other end, though, with Southby introducing Phoenix Karaka at goal defence for Sulu Tone-Fitzpatrick. The athletic 19-year-old made an immediate impact with her extra elevation. The Steel fell further behind but its ability to score quickly meant the game was always within reach.
Wendy Frew put her body on the line to snatch a pass away from her opponent and the Steel converted.
Having been outplayed for the majority of the game, suddenly the Steel led 50-47 with 15 minutes remaining. It hardly seemed fair, but having got into the position to win the match, the Steel showed its class to close out the game.
ANZ Championship
The Scores
Steel 73
Jhaniele Fowler 59 from 61, Jodi Brown 14/15
Mystics 63
Bailey Mes 37/46, Maria Tutaia 26/35
Quarter scores: 1st 15-16, 2nd 32-33, 3rd 50-47
