Analysis: Sam Stosur's mental game holding her back from tennis greatness

Australia's 4-0 whitewash loss to the United States in its Federations Cup tie in Brisbane over the weekend has once again brought into the spotlight the conundrum which is Australia's highest ranked female player, Sam Stosur.

Not many professional tennis players can boast a victory over arguably the best player in world, Serena Williams, but Stosur, currently ranked 26th in the world and once as high as fourth, had scored such a feat.

The Aussie shocked the world in 2011, not only by beating Williams in straight sets, but in a Grand Slam final in front of a raucous U.S. Open crowd, but the great conundrum that Australian tennis fans continue to ask themselves is why has Stosur not been able to consolidate her, ironically, consistently shaky form.

Over the weekend, in Australia's Fed Cup tie against the United States, Stosur was twice a set up against her lower-ranked American opponents. But, in typical Stosur fashion, she disappointed fans on home soil and lost the following two sets on both occasions.

Not only that, but Tennis Australia purposefully installed an Italian clay court to best suit Stosur's style of play - at a cost of 80,000 U.S dollars.

The 32-year-old might be entering the twilight of her career, but consistency - often an issue associated with younger players - is still her weakness.

Never before has she made it past the fourth round of her home Grand Slam in Melbourne, while, after looking as though she would take the tour by storm after finishing runner-up at Roland Garros in 2010 and winning the 2011 U.S. Open, she has made just one semifinal in the last four years.

Stosur has won eight titles on the women's tour, but has also lost 14 - underlining her frustrating inability to finish the job.

To her credit, Stosur has one of the most enviable physiques in the women's game, and it is evidenced in her game style. Her first serves often exceed 190 kilometers per hour and her mesmerizing forehand is one of the best on the tour when hit right.

But in big moments over her career, Stosur has wilted under pressure. For all the work she puts in on the practice courts, she has been unable to grasp the mental demons which seem to plague her at crucial points of almost every big match.

On Sunday, following her loss to Coco Vandeweghe, Stosur said her inability to close out crucial matches was "frustrating", particularly as she felt she was playing good tennis.

"It can be a very frustrating thing, obviously, and very disappointing. But I guess it's also a good thing - you'd rather play well and go down in a tough one than not put in a good performance," Stosur said.

"It doesn't necessarily make it any easier right now, but on the whole I'm playing good tennis. But you want to get those wins."

Where Stosur goes from here is the question on the minds of Aussie tennis fans. The world No. 26 has recently announced she would be ending her relationship with current coach David Taylor, who would be stepping down after the French Open later this year.

Like Chinese Grand Slam winner Li Na, Stosur could follow the path of hiring a coach to help her mental game later in her career.

At 30 years old, and seemingly on the decline, Li hired Carlos Rodriguez in a move which propelled Li up the rankings, curbed her poor on-court behavior and won her the 2014 Australian Open.

Maybe Stosur could also have a late-career renaissance and once again rise to the heights she often threatens - but fails - to hit. Endite