With only marginal fanfare, one of the most interesting players in modern tennis history retired two weeks ago.

Ana Ivanovic, 29, had twice been ranked No. 1 in the world and won the 2008 French Open as well as 14 other WTA titles.

How the willowy Serbian managed to do that seems almost beyond explanation, especially for those of us who saw her struggle over the final eight years of her career.

In an era when the women’s game has been dominated by big and physically powerful women, Ivanovic stood out — because she not only was thin, she seemed almost frail, and her game often reflected what should have been a strength-deficit impossible to overcome.

Patty-cake serve, limited pace, a shockingly weak backhand …

Yet there she was at No. 1 for 12 weeks in the summer of 2008, after her French Open victory.

How did she do it?

Grit, guile, quickness, a strong forehand, more grit, and more than a little luck as she filled a vacuum at the top of the women’s game, back in 2008.

Not since Tracy Austin, in 1980, had a top-ranked women’s player been less physically impressive.

Ivanovic entered women’s tennis with one clear advantage — height. She is 6-feet tall (Austin was 5-foot-5), and some believe her height was a factor in her skill on clay courts, where high-bouncing returns put the ball near eye level for her.

Into 2008, too, her serve was considered at least acceptable.

But she also benefited significantly from a moment in time in the women’s game when several strong players had recently retired or were hurt or in a rough patch.

Former No. 1 Justine Henin retired just ahead of the 2008 French Open, which she had won the previous three years.

Serena Williams had played sparingly in 2008, due to dental surgery and a back injury. She went out in the third round to Katarina Srebotnik.

Maria Sharapova was No. 1, due to Henin’s retirement, but she was not playing well, perhaps in large part due to a rotator cuff tear which required surgery later in the year.

Former No. 1 Lindsay Davenport pulled out of the French a few days before it started, citing an injury. Former No. 1 Amelie Mauresmo was losing early and often at the point in history.

Former No. 1 Kim Clijsters missed the whole of 2008 after giving birth. Venus Williams missed time with an undisclosed injury early in the year and lost in the third round to Flavia Pennetta.

And so on.

Women’s tennis was a mess, in May 2008, and Ivanovic took advantage, and more power to her.

She was not asked to beat a bunch of great players at Roland Garros. Her victories came over Sofia Arvidsson, Lucie Safarova, a not-quite-ready-for-prime-time Caroline Wozniaki, Petra Cetkovska, Patty Schnyder, Jelena Jankovic and Dinara Safina. Only Jankovic took a set off Ivanovic and Safina, the other finalist, was a one-year wonder rather like Ivanovic.

Then things pretty much fell to pieces. Ivanovic seemed to wilt under the pressure of being No. 1, losing four of her next eight matches after her French Open title.

But perhaps more important? The players with the physical tools to be No. 1 (Serena Williams, in particular) either came back from injuries or rocky play, and several others broke through for the first time, and they collectively pushed Ivanovic down the rankings.

By July of 2010, Ivanovic had plummeted to No. 64 in the women’s rankings, after losing in the first round at Wimbledon. Following the 2008 French Open, she failed to reach the quarterfinals in 17 consecutive grand slam events.

She fought her way back up into the top 20, on guile and moxie, and mostly stayed there the rest of her career, but she never won a second major.

Towards the end, her modest velocity decreased further, and to watch her play was almost painful, as she lobbed balls back at bigger and stronger players who passed her with ease.

In retiring, she said she had lost her enthusiasm for the game, in part because of her struggles with injuries in recent years, and did not expect to return to the game, not even as a coach.

She was known for never giving up, for her sportsmanship and for being a person competitors found it impossible to dislike.

Ivanovic, who recently was married to German soccer star Bastian Schweinsteiger, for 14 years was one of the faces of the women’s game and one of its great ambassadors.

And she had the heart of a champion, if not the build of one.

She will be missed.