Mihaela Buzarnescu was languishing outside the top 500 in the rankings at the start of last year but the Romanian has proved that persistence pays off at the French Open.

Blighted by injuries after showing such promise as a youngster, Buzarnescu looked to the future by signing up for a degree in sports science in her late 20s.

The powerful left-hander underwent knee surgery twice, but was still feeling the pain.

Buzarnescu got her head down during a two-and-half-year spell out of the game and was rewarded with a PhD late in 2016, so it appeared a career change was in the offing.

"When I had the first surgery before I stopped, I said that I didn't know exactly how it will be with the surgery, how it will be the rehab, and if it will be good. So that's when I started the PhD," she said.

Many would have thrown the towel in given the setbacks the Bucharest native had endured, but all of a sudden the left knee was not hampering her just over a year ago - as opponents in the Dutch tennis league discovered.

She reeled off 20 consecutive wins at ITF level, taking titles in Hungary, Turkey, Spain and Germany.

Buzarnescu surged up the rankings and made her grand slam debut at the US Open last year at the age of 29.

The late bloomer's rise has been so rapid that she is ranked 33rd in the world and seeded at Roland Garros, where she pulled off a shock by beating the well fancied Elina Svitolina in the third round on Friday.

Buzarnescu, who turned 30 last month, will come up against Madison Keys in the fourth round in Paris on Sunday. 

"I don't know how to pronounce her last name, so I won't say it," Keys said when asked about her next opponent, but she is now set to learn all about the Romanian. 

And it seems Serena Williams may not be the biggest comeback story of the tournament after all, as Buzarnescu continues to make up for lost time.