Australian Diamonds star Gabi Simpson out of Quad Series

Australia have been rocked by further injury on the eve of their high-stakes netball Quad Series double-header in London, with defender Gabi Simpson lowered by a leg injury.

Accomplished wing defence Simpson took a blow during a midweek practice match against England A and will miss the Test against New Zealand at the Copper Box on Sunday (AEDT) followed by a likely series decider against England a day later.

Simpson had been promoted to on-court captain for the series after regular skipper and goal shoot Caitlin Bassett suffered a fractured forearm ahead of the series-opening win over South Africa.

Shooter Caitlin Thwaites will take over as on-court captain while uncapped 21-year-old shooter Kiera Austin is added to the 12-strong squad.

Simpson's starting spot is likely to be claimed by Jamie-Lee Price, who impressed in the 62-45 win over the Proteas.

Coach Lisa Alexander said the twin injuries would provide a test of her team's leadership and ability to cope with adversity five months out from the World Cup.

"This situation will provide a great opportunity for not only Kiera ... but for the rest of the team to step up in their respective roles and to lead from the front," she said.

"We're building our momentum towards the World Cup and this provides a tremendous opportunity for our athletes to demonstrate why they should be in that team."

Australia are heavily favoured to maintain their run of dominance over New Zealand, having lost just once - in Hamilton last October - in the past 10 trans-Tasman Tests.

An England team at full strength hammered the Silver Ferns 54-41 last week and are confident they can repeat last April's defeat of Australia in the Commonwealth Games final.

Thwaites said both Tests would be challenging but the likely tournament-decider against the Roses would have the most riding on it.

"We want to kind of assert ourselves," she said.

"England knocked us off at Comm Games but if we can get another one up on them going into the World Cup, that'd be really great for us. We definitely know they want to do the same to us."