The match started with a twist as Styris was ruled out after injuring his hamstring bowling for the Hobart Hurricanes in Saturday evening's Australian Big Bash League.
The match started well for Marshall after winning the toss and putting the Aces in to bat in overcast conditions, and he was pleased to have both openers back in the shed by the sixth over.
But tenacious Aces skipper Gareth Hopkins (57 off 45) steadied the ship, assisted by Anaru Kitchen (27) before big-hitting Colin de Grandhomme smashed an unbeaten 66 from 30.
De Grandhomme's 80-run stand with Hopkins allowed them to take back firm control of the innings, and despite a small flurry of wickets at the death, the Aces would have been satisfied with their 180-5 total, as shower clouds began drifting over and conditions became more difficult.
The home batsmen struggled to get their chase going against a quality attack, with Kyle Mills and Michael Bates exerting pressure.
Two down at the halfway mark with the lingering threat of rain and a Duckworth-Lewis chart already in the hands of the coach, the Knights urgently needed to lift their run rate and launched into Kitchen, peeling 20 runs from the 15th over.
But sustained control from the rest of the Aces' attack snuffed out the Knights' remote chances of victory in the closing overs, Mills removing the dangerous Croft early in the penultimate over and fellow English pro James Foster falling to a spectacular diving catch behind the wicket from Hopkins.
To add injury to insult, Knights all-rounder Anderson was whisked off for X-rays of his wrist and didn't take part with the bat.
It was the fourth-placed Aces' first win in five games and the defending champions now have an ideal run home, needing to rack up back-end victories to squeeze their way into the top three.
Just three regular competition games remain for the Aces, the next against bottom side the Central Stags in New Plymouth tomorrow, followed by the struggling Canterbury Wizards and a second crack at the Stags.
The third-placed Knights, meanwhile, face the Wizards in Hamilton on Friday night, while the second-ranked Hell Wellington Firebirds meet frontrunners the Otago Volts that afternoon in Wellington.