The wing attack injured her right knee in the opening quarter of the 49-45 loss to the Northern Mystics in Dunedin on Sunday.
Steel physiotherapist Brett Woodley said Tairi was continuing to undergo tests to determine the full extent of the damage.
"Courtney has suffered an ACL injury but we are still uncertain as to the severity of it at this stage," he said.
"She will be going through a rehabilitation programme in the next few weeks and hopefully, it will respond well to that. The grade of the injury is still unclear but we certainly hope she will be back on the court soon."
Tairi is eager to return to the court but also suitably cautious.
"I've got to take some time to let it settle down and then do some rehab," she said.
"I'll be working closely with the physios to determine the full extent of the injury and work through the recovery process."
Because Tairi is a member of the national accelerant group, any future decisions will be made in conjunction with Netball New Zealand's medical team, Woodley said.
In her absence, Shannon Francois is likely to don the wing attack bib, Phillipa Finch shift to centre and Louise Thayer and Hayley Saunders jostle for the wing defence spot.
The Steel host the defending champion, the Queensland Firebirds, in Invercargill on Sunday. It is the first time the Steel has played in Invercargill since its opening match against the Waikato-Bay of Plenty Magic, on April 2.
