The 19-year-old Stephens won 6-3, 6-4 against the 2010 French Open champion. Stephens has advanced to at least the third round at three of her last four Grand Slam events. She's ranked a career-best 44th.
At 3-3 in the second set, Stephens broke Schiavone at love, the game ending on a double-fault. The Italian had seven of those in the match - five in her first service game.
Stephens had double match point at 5-3 against Schiavone's serve but couldn't convert. Trying to serve out the match, she fought off a break point then clinched the victory with a forehand winner down the line.
The 32-year-old Schiavone pulled out of New Haven last week because of an illness.