By July 2012, she had cracked the top 50. Maybe, after some false dawns regarding the next great American female, this was the real thing? The hype went into overdrive at the 2013 Australian Open, when she reached the last four after an epic victory over Serena Williams.
Williams reacted sourly after the defeat which confirmed two things; the supposed mentor-pupil relationship between the two had been overstated, and Stephens was a contender.
She reached the second week of all four Grand Slams that year, including a quarter-final at Roland Garros, and hit No 11 in the world.
But then, as happens to many breakout stars on the tour, she plateaued. Stephens was no longer an unknown and instead became a prize quarry. She slipped out of the top 20, then fell out of the top 30.
There were still moments of glory, but not the exponential improvement that had been expected.
Things turned in the second half of 2015. After being eliminated at the semifinal stage on four previous occasions, she made her first final at the Citi Open - and won it.
Before that week, she had played 84 tournaments and not won any, unique among the top 30 players.
Yesterday, she coped well with Naomi Broady, who again raised her game well beyond her ranking, subduing the Brit 7-6 (6), 6-3 in 96 minutes.
In other matches, Tamira Paszek outlasted Kirsten Flipkens 6-4, 6-7 (3), 6-3 in the first quarter-final, in a match that stretched to almost three hours and last night the third seed Caroline Wozniacki easily accounted for Alexandra Dulgheru 6-1, 6-0 to firm as favourite for the title.
The earlier clash followed a similar script, with German Julia Goerges eventually prevailing over Japan's Nao Hibino 7-6 (3), 6-2, 6-4 in more than two hours.
Goerges, who has been as high as No 15 in the world, always looked the likely winner but took a long time to get going.
World No 66 Hibino was surely one of the most low profile quarter-finalists in the tournament's history, having spent most of her career playing lesser ITF events.
But she showed admirable fight, as well as the swift movement typical of many Japanese players to push Goerges much harder than expected.
Results
Quarter-finals
Julia Goerges (GER) bt Nao Hibino (JPN) 6-7(3) 6-2 6-4.
Tamira Paszek (AUT) bt Kirsten Flipkens (BEL) 6-4 6-7(3) 6-3.
5-Sloane Stephens (USA) bt Naomi Broady (GBR) 7-6(6) 6-3.
3-Caroline Wozniacki (DEN) bt Alexandra Dulgheru (ROU) 6-1 6-0.
