The 22-year-old picked up a concussion after a heavy collision with Northern Stars defender Elle Temu during the third quarter of Saturday's game in Dunedin.
She thudded hard to the ground and the England international was left clutching her head.
She was initially treated at the side of the court before leaving the stadium in a wheelchair.
By then she had recovered enough to wave at the 2000 or so fans who had showed up to watch the match which the Stars won 53-43.
Fisher was reassessed by Steel's medical team yesterday afternoon and a concussion diagnosis has been confirmed.
Steel head coach Reinga Bloxham said Fisher would not travel for the team training sessions in Dunedin this week or be available for the fixture against the Magic.
“George is under strict orders to rest until she is symptom free and, as a team, we are supporting her to do exactly that,” Bloxham said.
“It is always a blow to lose a key player to injury but we need to ensure she’s 100% fit before returning to the court.”
Fisher will be reassessed again next Tuesday.
“We train for all scenarios so, while we will miss George and everything she brings on and off the court to our environment, we are prepared for this and determined to continue our momentum.”
Fisher stuck a late shot to seal a tense 59-58 win against the Magic when the two sides last met.
She initially missed but swooped on the rebound and drilled her second attempt.
Fisher is the second leading scorer in the competition with 415 goals from 460 attempts.
Ten of those misses came in the last game when she produced an uncharacteristically sloppy shooting display.
Kiana Pelasio replaced Fisher when she left the court and the Steel really struggled in the last quarter.
The Stars outscored their opponent 17-9, stretching a two-goal lead into a comfortable 10-goal win.
The Stars (25 points) extended their lead at the top of the competition standings with the win.
The Steel (18 points) is still well-placed in third equal. But it will not want to be without its ace sniper for long.
Last year the Steel lost two shooters to injury — Georgia Heffernan and Jennifer O’Connell.
They both required knee surgery.
