\u201cI think it\u2019s very easy to be in a position where things are flowing, you know,\u201d Sharapova said. \u201cYou\u2019re doing all the right things, she\u2019s making a few errors, you\u2019re comfortable \u2014 easy to get complacent, and, you know, complacency is not great. I was glad that I did the right things from the beginning till the end.\u201dUp next for Sharapova is Rebecca Peterson, who beat Sorana Cirstea, 6-4, 6-1.John Isner hit more aces than his opponent, 47-40. He delivered more total winners and finished with more overall points, too. What Isner failed to do for the first time in his career was beat an American foe at a Grand Slam tournament, and now the highest-ranked man from the U.S. is gone from the Australian Open.Reilly Opelka, ranked just 97th, earned his first victory in a main-draw match at a major by edging Isner in four tiebreakers 7-6 (7-4), 7-6 (7-6), 6-7 (7-4), 7-6 (7-5).If anyone is Isner\u2019s equal when it comes to big serving, though, it\u2019s Opelka, a 21-year-old based in Florida who at 6-foot-11 is an inch taller than Isner.Defending champion Caroline Wozniacki saved a break point in the opening game but there was little trouble to follow as she beat Alison Van Uytvanck, 6-3, 6-4, in the first round. Wozniacki, who saved both break points she faced, clinched the match on her third match point with a forehand to the open court.Fifth-seeded Sloane Stephens ended a three-match losing streak in first-round matches at Melbourne Park with a 6-4, 6-2 win over her fellow American Taylor Townsend.Stephens lost in the first round of the Australian Open in 2015, 2016 and 2018. She missed the 2017 tournament here after having foot surgery and went on to win the U.S. Open later the same year.