Williams defeated 17-year-old Caty McNally in three sets.
Serena Williams defeated Caty McNally in three sets (5-7, 6-3, 6-1) on Wednesday, extending her hopes of earning her 24th Grand Slam title with a second-round U.S. Open victory.
McNally outlasted Williams after the first ten games, claiming the first set 7-5. The 17-year-old American reeled off three points in a row despite facing a 0-40 disadvantage on her serve, clinching the set on a 103-mph serve onto the centerline.
After losing the first set, Williams took a 5-2 lead in the second set before McNally staved off four set points to make it 5-3. Willams then gained a fifth set point and converted it with a backhand volley winner, claiming the second set 6-3.
Williams dominated the third set, scoring ten straight points and dropping just five en route to a 6-1 win.
Williams is now 19-0 in second-round matches at the U.S. Open after Wednesday's win. The six-time tournament champion took down Maria Sharapova in straight sets (6-1, 6-1) on Monday.
McNally won the doubles title at the Citi Open in Washington earlier this month with 15-year-old French Open breakthrough star Coco Gauff. She earned her first Grand Sam main-draw victory by defeating Timea Bacsinszky on Monday.
Williams will face either Karolina Muchova or Su-Wei Hsieh in the third round on Friday at 11 a.m. ET.