MASON, Ohio -- World No.1 Iga Swiatek kicked off her Western & Southern Open campaign with a 6-4, 7-5 win over Sloane Stephens to advance to the Round of 16. The victory is Swiatek's tour-leading 50th win of the season, including her two wins at the Billie Jean Cup. 

Swiatek will face Madison Keys, who defeated Jelena Ostapenko 6-4, 7-5, next.

Highlights: Keys d. Ostapenko 

In the first meeting between the two Slam champions, Swiatek broke Stephens six times over the course of the match. While the performance was not as clean as Swiatek would have preferred -- she hit 17 winners to 25 unforced errors -- Swiatek was able to keep Stephens at bay. She held the American to just nine winners in the match. 

"I'm pretty happy that I started well, both sets," Swiatek said. "I had some trouble closing it earlier, but I'm really happy that in those important moments I was able to refocus again.

Asked to reflect on her best wins of the season, Swiatek cited her variety of three-set comebacks.

"Well, for sure those matches maybe in Indian Wells, those three sets against Simona and Angie," Swiatek said. "Yeah, it was pretty tricky, but also, at Australian Open when I could come back after losing first set, that really gave me a lot."

Here are some fast facts on Swiatek's 50th win:

2019: The last time a player tallied 50 wins in a season. That season, Ashleigh Barty posted a tour-leading 56 wins en route to being named WTA Player of the Year. Kiki Bertens and Karolina Pliskova also crossed the 50-win threshold that season.

39: Number of straight-set wins for Swiatek this season (78.0%).

6: Number of losses Swiatek has had this season.

0: Losses in 2022 for Swiatek when she wins the first set, going 33-0. 

9: Number of matches Sloane Stephens has played against a reigning WTA World No.1. With her loss to Swiatek, Stephens drops to 0-9. 

24: Wins at WTA 1000s this season for Swiatek, the most since Simona Halep won 26 in 2017.

1: Player who has a higher winning percentage than Swiatek at the WTA 1000 level. With a 40-11 record at the WTA 1000 level, Swiatek's winning percentage is 78.4%. Only Serena Williams has a higher strike rate at 83.1%.

8: Years since a player won seven or more titles in a single season, which Serena Williams did in 2014. Swiatek has already won six this season.