But she hasn't really threatened the big time since her run to the 2013 Australian Open semifinals, when she first shot to fame after a quarter-final victory over Serena Williams.
Stephens hasn't cracked the top 20 since August last year and reached her first WTA final only in September, after falling at the semifinals on seven occasions.
In tennis terms, she's no longer a young gun, turning 23 in March. At the same age, the big three in the ASB Classic field had all reached Grand Slam finals (Venus Williams had won four titles from seven finals, Ana Ivanovic one from three, and Caroline Wozniacki one final) and Serena had already collected five Grand Slam trophies from six finals.
There aren't many doubts over Stephens' ability - she is a tremendous athlete, with great power from the baseline and ability at the net - but too often hasn't been able to find her best performances when it matters. She's also been guilty of wild swings in form and frustrating losses to players ranked well below her.
But there is hope. Her breakthrough WTA title in Washington was an important milestone and she was much more consistent in 2015, after reuniting with former coach Nick Saviano.
Most of her defeats were against players from the next tier up and she also twice pushed Serena Williams to three sets last season, at the French Open and Indian Wells.
Indeed, the emerging rivalry with Williams has defined her career in some ways. The older American was seen as a mentor until a public feud in 2013 after Stephens' upset in Melbourne became one of the more riveting tennis stories that year.
Williams didn't take defeat to the youngster well, posting a cryptic "I made you" tweet after the match before apparently cutting all contact with her compatriot.
"She's not said one word to me, not spoken to me, not said hi, not looked my way since Australia," Stephens told ESPN The Magazine a few weeks after the match. "People should know. They think she's so friendly and she's so this and she's so that - no, that's not reality. You don't unfollow someone on Twitter, delete them off of BlackBerry Messenger. I mean, what for? Why?"
Not many doubted the veracity of Stephens' comments but she was heavily criticised in the media for speaking her mind, and an apology later appeared on Twitter.
"Guilty of being naive. Much respect 4 @serenawilliams, a champ & the GOAT. We spoke, we're good. ONWARD! #lifelessons."
Unfortunately those trials by media, which can be unforgiving in the tennis world, have taken away much of the refreshing honesty about her, and any willingness to provide much insight about her game or life. An interview with the Herald on Sunday yielded little, apart from a string of cliches: 2015 was a "pretty good year" and she is "looking forward to building on a lot of things learned". The Washington triumph was "exciting" and Stephens is "hoping to be in that position again". She tries "to focus on improving each time [she plays]" and enjoys "the competition and the challenge of working on my game".
Asked how she can beat the big names more regularly, she responds that she has "got to keep focusing on improving my game and all the details that will help me continue to improve". And the Williams sisters are "great tennis ambassadors" and she is "fortunate to be their countrywoman".
Tennis players, with daily press conferences after every match, are subjected to more media than perhaps any other sportspeople but it's a shame Stephens seemed to have lost much of the candour that made her one of the WTA Tour's more interesting characters.
Hopefully in the New Year, she can sparkle on and off the court in Auckland.
