The Chelsea forward missed Australia's opening two games with a calf injury, but has declared herself available for their crunch clash in Melbourne on Monday that they must win to guarantee a place in the round of 16.
Gustavsson said he would meet with medical staff later Sunday ahead of further tests on Kerr scheduled for Monday.
"Everyone involved in sport knows that with calf injuries it's one thing that you're available, but there's also risk when you come back from a muscle injury," he said.
"So we need to balance how many minutes she is available, what are the risks if we go through to the play-offs.
"So a lot on the table to discuss and we probably won't know how we are going to use that until we are coming into the stadium tomorrow."
The Matildas battled past Ireland 1-0 before a stunning 3-2 upset at the hands of Nigeria, meaning they need to beat Tokyo Olympic champions Canada to make sure they stay alive and Kerr's return would be a massive boost.
Her replacement in their opener against the Irish, Mary Fowler, also missed the Nigeria defeat with a concussion and a decision on her will similarly be left until late.
"Mary trained fully today, but we need to reassess tonight how she feels, because it's a head injury," said the coach. "Obviously I hope it's a thumbs up."
Canada, who played out a sluggish goalless draw with Nigeria in their opening match and then rallied from behind to beat Ireland 2-1, will power into the last 16 with a win or draw in the high-stakes Group B clash.
Move on
Canadian coach Bev Priestman called on her team to be brave against Australia and put any noise around Kerr aside.
"There's a lot around about what might come up in front of us, but ultimately I know this team and if we turn up, we can go and get three points," she said.
"The focus is to be brave and bring what we bring and bring it well."
While Kerr's fate has dominated headlines in Australia, Priestman insisted it had not affected Canada's preparations.
"Have I spoken about, 'Is she or isn't she?'
"No I haven't," she said. "We've spoken about what it takes to beat Australia because Australia is not just Sam Kerr.
"I want to get three points, that's all I'm focused on, to move on and into the next game. If that means we knock out the co-hosts, then we knock out the co-hosts."
Even if Canada lose, it will not necessarily be the end of the road. But they will need Ireland to beat Nigeria with goal-difference then coming into play.
Similarly for Australia, a loss and they are out of the tournament. But a draw coupled with Nigeria losing and it would also be decided by goal difference.
