INDIAN WELLS, CA, USA -- Reigning US Open champion Sloane Stephens is smoothly rounding into form, as the No.13 seed clinched a second-round win over two-time major champion Victoria Azarenka of Belarus, 6-1, 7-5, at the BNP Paribas Open on Sunday.

The American handily overcame a dire disadvantage in their head-to-head history -- Azarenka had won all six sets in their three previous encounters, which were all at the Australian Open, in three consecutive years from 2013 to 2015.

But on the hardcourts at Indian Wells, Stephens flipped the script, easing to victory in 75 minutes, one day after their second-round match had been postponed due to incessant rain on Saturday night. After suffering through an eight-match losing streak following her US Open title, Stephens has now won three of her last four matches.

"I'm feeling a lot better, playing better," Stephens said to the media, following her victory. "I got some matches in Acapulco last week. And to get a win here, it's not easy having a bye and then playing somebody who has already played a match. Feeling good. Everything's all good."

"I'm going to listen to my body and make sure that I can do everything possible not to get injured again and make sure that I take care of myself mentally and physically the best way I know how," Stephens continued.

Stephens was motivated and persistent en route to the win. Her forehand was pointedly strong, and she had 15 winners in the match, outpacing her 11 unforced errors.

Two-time BNP Paribas Open champion Azarenka was playing her first tournament since Wimbledon of last year, and claimed her first win in eight months over Great Britain's Heather Watson in the opening round. But, against Stephens, Azarenka failed to hold serve in her first five service games, and was undone by 24 unforced errors and five double faults.

"Obviously a lot of work to do," Azarenka told the press afterwards. "For me, the most important is to have a clear head, which obviously right now is not. Once I figure all my stuff outside of the court, I'll be able to focus and be 100 percent when I'm on the court to be there."

Stephens dropped her serve in the opening game of the match, after Azarenka crushed an overhead and a searing backhand service return to break the American. But that would be the only moment of glory for the Belarusian in the opening frame, as Stephens went on a six-game run that took her to a one-set lead in 26 minutes.

While Stephens was being aggressive, combining powerful forehands with passing shot and volley winners, Azarenka never gave herself a chance in the first set. The former World No.1 could only take 40 percent of points on her first serve, and did not win a single point on her second serve in the opener.

"I felt like I started the first game well, and then kind of everything just went away," said Azarenka. "Started to be so many mistakes and quick, you know. I kind of didn't know what I was doing out there."

Azarenka started the second set with another break of the American's service, but Stephens once again evened the score at 1-1 in the very next game, by breaking Azarenka at love. The players exchanged breaks once more en route to 2-2, before Azarenka finally held her service on her sixth attempt to eke ahead in the set, 3-2.

At that point, Azarenka hit a patch of games where she held her serve comfortably, exhibiting the form which has brought her incredible success throughout her career. But Stephens, a major champion herself, refused to succumb to the Belarusian's improved form.

Serving down 4-5, Stephens fell behind 0-30, putting her two points away from a third set, but the US Open titlist held firm for 5-5, as the unforced errors began to re-appear in Azarenka's game. Indeed, after missing that small window, Azarenka lost the spark she showed in her previous service games.

"I found a little bit better rhythm in the second set, found a little bit more fight," said Azarenka. "But just, you know, really low quality consistency from me today, and it's tough to win matches like this."

Serving at 5-5, a double fault and a forehand error quickly put Azarenka behind 0-30, and Stephens hit an excellent backhand passing shot to reach triple break point. She only needed one chance to reclaim the break advantage, and coolly served out the match in the following game, for a historic victory in her career.

Stephens will face No.20 seed Daria Kasatkina of Russia in the third round. The Russian, freshly into the Top 20 of the WTA rankings, defeated Czech Katerina Siniakova on Saturday, 6-2, 5-2, ret.

"I played [Kasatkina] on clay in Charleston," Stephens recalled. "I was down a match point. We played actually a pretty good match, so I think it will be interesting. Obviously the courts here suit both of our games pretty well. So I think it will be another good match, and I'm looking forward to it."