French Open 2019: Serena Williams overcomes first-set wobble to beat Vitalia Diatchenko

The victory was her 800th career win in the main draw of a tournament - but also only her second match since the Miami Open in March.

Williams looked sluggish and as if she was struggling to move in the opening set, allowing her 28-year-old opponent to surge to a lead.

But the 23-time Grand Slam champion was resurgent in the second, drawing on her reserves of power.

The statistics spoke for themselves at the end of the match - Williams hit almost equal numbers of winners and unforced errors, 25 compared to 24, but 20 of those winners and ten of the errors came in sets two and three combined.

The 10th-seeded American peppered Court Philippe Chatrier with unforced errors in an ugly opening set before finding her range to set up a meeting with Japan's Kurumi Nara or Slovenian Dalila Jakupovic.

"I'm just happy to win today," the American said after her 800th tour-level victory.

The three-times Roland Garros champion is looking to emulate Margaret Court, who claimed 24 majors spread across the amateur and professional eras.

Williams's haul started at the U.S. Open 20 years ago but she has not won a major since she beat her older sister Venus in the Australian Open final in 2017.

She produced a see-saw display in an half-empty stadium on Monday, struggling to adapt to windy conditions in chilly weather.

Diatchenko broke in the fifth game with a crosscourt backhand winner to open a 3-2 lead, and won on her opponent's serve again in the seventh game to secure the opening set.

Then Williams fired up the engine and raced to a 3-0 lead in the second set, losing only one more game as Diatchenko faded away.