Stephens, 19 and from Florida, is ahead of her schedule with a berth in the top eight of a major already ticked.
Her job is to slow down the hype.
Stephens lost to Williams by a respectable 6-4 6-3 at this month's Brisbane International and insists Wednesday's meeting will be simply another routine match.
"You've just got to go and treat it like another match," Stephens said after the 29th seed outlasted Serb Bojana Jovanovski in three tight sets on Monday.
"It wasn't like, 'Oh, my God, I played Serena, I'm going to be so great at all these other things because she just taught me so much'.
"It was just another match, regular match. Little things that you just take and move on.
"That was two weeks ago now, three weeks ago ... I played seven other matches or eight other matches, so I'm kind of past what happened then."
Williams' latest victim was Russian Maria Kirilenko, who she blasted 6-2 6-0 to reach the quarter-finals as she bids for a sixth Australian title.
The 31-year-old said she would be better prepared for the youngster on Wednesday following their Brisbane encounter.
"I took a lot from that match - she plays well," Williams said. "Like I said after the match, she can be the greatest player."
While Stephens might be the next American to strut the world stage, Williams won't be giving her a hand up just yet.
"It's hard to be a real mentor when you're still in competition," she said.
"I feel no responsibility. I doubt she has any expectations of me to be responsible for anything.
"I'm here to compete and do the best I can."