Nothing comes easy to Maria Sharapova on her grand slam return after a doping ban, but the Russian's mix of grit and power were enough to see off American teenager Sofia Kenin 7-5 6-2 in the third round of the US Open on Friday.

Sharapova, who made her comeback in April after a 15-month ban following a positive test for meldonium, battled through the first two rounds and it seemed that she would also struggle against the 18-year-old Kenin.

Hitting winners and unforced errors in almost equal measure in the opening set, the former world number one dug deep to take the advantage.

Kenin's tank was empty in the second set and Sharapova, who next faces Latvian 16th seed Anastasija Sevastova, opened up a 3-0 lead and ended the contest on the first match point when the American sent a backhand wide.

"We had never faced each other and she came out having nothing to lose and it's always dangerous so I'm happy I went through," said Sharapova, who won her only U.S. Open title in 2006.

Sporting a leather-collared black dress encrusted with crystal, Sharapova made a rock star entrance on a packed Arthur Ashe Stadium to close the night session.

But it was all sweat in a rough start for the former world number one as she made nine unforced errors in the first three games.

"I did not see the ball too well at the beginning of the match, I wasn't getting the shots that I wanted," she said.

The flurry of unforced errors continued but in the 12th game, the Russian broke to bag the opening set when Kenin could not retrieve a powerful flat forehand and then raced through the second set.

Maria Sharapova of Russia hits to Sofia Kenin of the USA.