Defender Anna Harrison and shooter Cathrine Latu inspired the visitors to the four-goal win with superb individual performances.
Latu has missed just three goals in seven games and was flawless again last night, drilling 35 goals from 35 attempts.
Harrison was just as accurate down the other end, picking off nine intercepts in a remarkable effort.
Despite the relatively close nature of the final score, the Mystics controlled the fixture and always seemed destined to win.
A poor opening quarter from the home side rather sealed its fate, Steel co-coach Janine Southby said.
"We had a really disappointing start," she said. "It was something we've talked about and it was one of the areas we've been working on, but it let us down again.
"We are getting enough turnover ball but we're not converting it. When you're playing a team like the Mystics, if you don't score what ball you get off them, then they will score.
"It was another one of those games that got away from us. We know we are good enough but we have to close these games out."
Earlier, Steel captain Jodi Brown's first touch of the ball was a wild pass which found the media bench rather than its intended target and set the tone for the home side.
The passing was sloppy and inaccurate and it allowed the Mystics to take control of the opening period.
Experienced centre Temepara George provided one of the highlights with a superb fake and then a pinpoint pass which found Latu right under the net.
It was yet another example of her fantastic vision.
Harrison also had a storming quarter, nabbing four intercepts, and the Steel really struggled to feed its experienced shooting combination of Brown (19 from 25) and Donna Wilkins (26 from 28).
The Mystics led 15-10 at the break, a lead which would later prove decisive.
Latu, despite her robust frame, is incredibly light on her feet and demonstrated some marvellous footwork when she swivelled and lobbed a shot in before tumbling out of court midway through the second spell.
Trailing by seven goals at halftime, the Steel's coaching staff opted to make a change.
Louise Thayer came on at wing attack for Hayley Saunders.
The change, though, did not address the major issue.
The Steel was losing too much ball on attack and perhaps needed to introduce back-up shooter Te Paea Selby-Rickit.
Thayer justified her inclusion with a busy performance, and under-rated defender Demelza McCloud got in front of Latu to poach some good possession for the Steel.
But despite an improved quarter the Steel was unable to make any inroads into the deficit.
Mystics coach Debbie Fuller dropped Tutaia to the bench for the final period with Grace Rasmussen preferred.
Rasmussen promptly missed her first attempt at goal and the Steel capitalised on the turnover, trimming the gap to four.
But Harrison's athleticism and Latu's accuracy stymied any potential comeback, although the Steel did win the last quarter 13-10.
Steel midcourter Courtney Tairi injured her left ankle with about 4min left in the first stanza and was not sighted on court again.
In other matches yesterday, the Adelaide Thunderbirds had a convincing 60-43 win against the West Coast Fever in Adelaide to go to the top of the competition table.
They replaced the Melbourne Vixens, whose six game unbeaten run this season came to a surprise end with the New South Wales Swifts recording a 55-52 win on their home court.
ANZ Championship
The scores
Mystics 49 (Cathrine Latu 35 from 35, Maria Tutaia 13/19, GraceRasmussen 1/3)
Steel 45 (Donna Wilkins 26/28, Jodi Brown 19/25)
Quarter 15-10, halftime 28-21, third quarter 39-32.
