"We are really conscious of players needing to be able to deliver the performance requirements of the team in the demands of tournament play."
Southby said it was important to the Silver Ferns to have Cullen fully fit with next year's Netball World Cup in England a key event.
"It's difficult because this is also about player welfare and having Kayla looking further ahead with a major tournament next year."
The medical team will now be working with Cullen over the coming days to determine the best course of action to ensure Kayla is back on court as quickly as possible.
It is not the first time the 26-year-old has been ruled out of a major netball event, having missed the Netball World Youth Cup in 2013, due to a ACL knee injury, which saw her sidelined for 12 months.
Her strong defensive qualities, versatility and genuine athleticism meant she was back in the black dress for the Netball World Cup in Sydney in 2015.
Cullen missed much of last week's Taini Jamison Trophy in Auckland, playing just three quarters against the Fiji Pearls.
Read more: Netball: A new low? Silver Ferns lose to Jamaica again
Kersten, who plays for the Te Wānanga o Raukawa Pulse, can cover both wing defence and centre and has played three Tests for the Silver Ferns including two appearances last week.
New Zealand opens their Commonwealth Games campaign against Uganda on April 5.
New Zealand Netball Team
Katrina Grant (Captain)
Maria Folau (Vice Captain)
Ameliaranne Ekenasio
Temalisi Fakahokotau
Shannon Francois
Kelly Jury
Grace Kara
Claire Kersten
Bailey Mes
Te Paea Selby-Rickit
Samantha Sinclair
Michaela Sokolich-Beatson