NEW YORK -- Maria Sharapova fought off a tough challenge Friday from American Sofia Kenin and then addressed a bigger foe -- the perception that the US Open is playing favorites.

Sharapova responded Friday to comments from Caroline Wozniacki, who complained after she was eliminated that Sharapova was scheduled for Arthur Ashe Stadium while she played on an outer court.

"That's not what matters to me," Sharapova said following her 7-5, 6-2 victory over the 18-year-old Kenin. "All that matters to me is I'm in the fourth round. I'm not sure where she is."

Sharapova, given a wild card by the U.S. Tennis Association into her first Grand Slam tournament since a 15-month doping ban, has played all three matches on the main court.

Wozniacki, the No. 5 seed, had said that Sharapova's court placement was a poor example following her second-round defeat Wednesday in a match that was scheduled for an outside court and eventually moved to another late in the day.

"With regards to scheduling, as you know, I don't make the schedule," Sharapova said. "I'm a pretty big competitor. If you put me out in a parking lot of Queens in New York City, I'm happy to play there."

She is usually reserved for the top players. Sharapova is a five-time Grand Slam champion, but she is unseeded here with a ranking that has tumbled to No. 146 following her suspension.

"When you look on center court, I understand completely the business side of things and everything," Wozniacki told Ekstra Bladet TV of Denmark. "But someone who comes back from a drug sentence and performance-enhancing drugs and then all of a sudden gets to play every single match on center court, I think that's a questionable thing to do."

On Friday, Sharapova struggled at times with the counterpunching, moonballing Kenin, who committed less than half of Sharapova's 33 unforced errors.

"I wasn't surprised with the way she came out and competed," Sharapova said. "She was down I believe a few match points in the previous match. She's a grinder. She'll get many balls back. Despite not having the experience, she's a tough player."

Sharapova eventually prevailed on power, ripping 36 winners to Kenin's six. Sharapova next faces 16th-seeded Anastasija Sevastova of Latvia, who earlier downed Donna Vekic of Croatia 6-2, 6-3.

Venus Williams is also into the fourth round of another major after beating Maria Sakkari of Greece 6-3, 6-4.

It was Williams' 74th win at the US Open, breaking a tie with Steffi Graf for fourth most by a woman in the Open era, according to ESPN Stats & Information.

The No. 9 seed reached the second week for the seventh straight major, the longest active streak in women's tennis. It's the first time since 2010 that she has reached the fourth round in every major.

However, Williams was eliminated earlier Friday from a chance at the No. 1 ranking when Garbine Muguruza reached the round of 16.

Third-seeded Muguruza, this year's Wimbledon champion, defeated 31st-seeded Magdalena Rybarikova 6-1, 6-1.

Two-time Wimbledon champion Petra Kvitova advanced 6-0, 6-4 over 18th-seeded Caroline Garcia.

Muguruza and Kvitova will meet in the fourth round.

American Sloane Stephens, 24, is into the US Open's fourth round, something she last did in 2013. Now she is into the second week at a major for the first time since the 2015 French Open.

Information from the Associated Press was used in reporting.