Free-rolling following emergency surgery last April to have a cyst the size of a tennis ball removed, Collins is hoping to become the latest surprise grand slam champion when she takes on Barty at Melbourne Park on Saturday night.

Collins powered her way into the decider with a 6-4 6-1 demolition of world No.9 Iga Swiatek on Thursday after Barty trounced Madison Keys 6-1 6-3 to become the first Australian woman to reach the Open singles final in 42 years.

But while Barty was the bookmakers' favourite well before a ball was hit this summer, few punters could have imagined world No.30 Collins making the title match.

After endless health scares during high school, including testing positive for an autoimmune disease, passing a kidney stone and frequent respiratory infections, the American was diagnosed with endometriosis last year.

Even after successful surgery, the 28-year-old has had to be vigilant and disciplined to keep herself in check.

Tennis was almost the least of her concerns or priorities.

"To be able to get back to this level and be able to compete like the way I have been and being able to be as physical as I have has been so rewarding," Collins said.

Now, though, Collins is one tantalising win away from achieving her childhood dream of becoming a grand slam champion after hitting her straps in Melbourne once again.

An Open semi-finalist three years ago and the most recent conqueror of Barty in Australia, Collins is taking heart from the recent trend of shock grand slam winners.

Swiatek bucked the odds to win the 2020 French Open, while Barbora Krejcikova was also unseeded when she won Roland Garros last year.

An even greater surprise came at last year's US Open when, in only her second major and ranked 150th, teenager Emma Raducanu became the first qualifier ever to win a grand slam.

"One of the special things on the women's side of the game is the depth across the board," Collins said.

"There's been so many women in the last couple of years who won slams that were not expected to win slams, and that gives hope to all the players.

"Whether you're outside the top 50 or the top 100, or if you're in the top 10, everyone has a chance of making deep runs.

"I've used that mentality and just tried to do the best I can, and tried to believe in how I'm playing."

Barty leads 3-1 in the head-to-head ledger against Collins.

But two of those losses went to three sets, and Collins was the victor at their most recent meeting - the Adelaide International last year.

"Every time we've played we've battled, and they've been some really fun matches," Collins said.

"Even the matches I've lost have been some of my most memorable moments on court because of the way we were battling and going back and forth.

"Something I really admire about Ash's game is her variety, and playing the different game styles than pretty much all of the players on tour.

"There's not too many that use the sliced backhand the way she does, and have the big serve the way she does."

Australian Associated Press