Staff members are never supposed to be in the same space with tigers, he explained.
A few zoo visitors were present and witnessed the attack.
The keeper was rushed to a nearby hospital following the attack by a tiger called Sanjiv and remains in critical condition.
"Sanjiv this morning did exactly what a tiger would when something comes into his territory", Mr Wiley said, adding there was "absolutely no consideration to euthanise Sanjiv."
A spokesperson said the zoo, which is 60 miles west of Kansas City, had been placed on lock down while the unidentified woman was taken for treatment.
After the animal arrived at Topeka, the zoo wrote on Facebook: "Sanjiv, a male Sumatran tiger, joined us at the Topeka Zoo this evening as a recommendation from AZA's Species Survival Plan".
The female zoo keeper who was attacked Saturday by the male Sumatran tiger under her care received major lacerating and puncture wounds, Topeka Zoo Director Brendan Wiley confirmed Saturday. We will update this story as more details become available.
Wiley is not releasing the name of the keeper, however he noted she was the tiger's primary keeper.
According to Wiley, the and Sanjiv were both in the outdoor tiger enclosure at the same time when the attack occurred and that "there really isn't a circumstance where they would be in the same space".
"It was all right there- kind of on the other side of the glass - if you can picture viewing that at our tiger viewing window", Wiley said.
"Nothing is going to happen to our tiger", Ms Hadfield said.
A spokeswoman for the City of Topeka also told CNN that the zoo staff member was "awake and alert" when she was transported to the hospital.