But the storybook tale played out just that way as the 24-year-old American won for the 15th time in 17 matches, defeating fellow American and best friend Madison Keys 6-3, 6 -0 in Saturday's US Open women's final.
Stephens, who had won only $310,000 this year, took a top prize of $3.7 million after learning much about herself and her tennis passion since being hurt last year.
"I'm not just going to let them take it from me. I'm going to make sure I give everything I have, and I leave everything on the court at all times, no matter what."
It's a determination bred in frustration after being forced to watch the Australian Open from her couch unable to walk after surgery in January. She still needed a walking boot in June.
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"I was super limited. I was walking on a peg leg, so that whole 15 weeks was super tough," Stephens said. "I think that was my toughest time."
"My head is a little clearer, if that makes any sense," she said. "Before, I was playing well. I had won a couple tournaments. But being injured gave me a whole new perspective on tennis, on life, and just in general."
Stephens is the daughter of former NFL player John Stephens, who played five seasons with the New England Patriots before joining Green Bay and Kansas City. His final season came just months after Sloane was born.
He died in a 2009 car accident. Sloane turned professional just weeks later.
Unsure of her strength, she tested her limits and reached US Open semi-finals at Toronto and Cincinnati, finding her skills quickly recovering into top form.
"When I came back from injury, I didn't have all of my tools. I didn't know if I was going to be able to run down every ball, didn't know if my power and timing was still going to be there. I didn't know if everything was still going to be right," she said.
Stephens made her best prior Grand Slam run to the 2013 Australian Open semi-finals.
"I was a baby then. I didn't know as much as I know now. A lot of life has happened. I have been through a lot," Stephens said.
"I don't regret it. Everything happens for a reason. Maybe I was a baby. Maybe I was too young. Who knows? I'm just happy to be playing.