Though tennis is not much of an underdog sport, something unusual has occurred at the 2011 French Open: all four top men's seeds have made the semi-finals.

And there are storylines for each star as they try to win the title at Roland Garros.

Novak Djokovic embarks on history with his improbable winning streak. Rafael Nadal tries to tie Bjorn Borg with six total French Open titles. 29-year-old Roger Federer attempts to prove he is still in the same class with younger stars Djokovic and Nadal. Andy Murray chases after that that first and elusive grand slam title.

While all four contenders have a reasonable shot at winning the Paris tournament, Djokovic has the edge with his 43-match winning streak going into Friday's duel.

Federer will have his eye on putting an end to the streak, but has more on his mind than just Djokovic.

The plan is trying to get a step further and into the finals of the French Open. At the end of the day, that's, for me, the big picture, and that's why I entered the French Open. It wasn't to stop Novak, said Federer after his quarter-finals victory over ninth-seed French star Gael Monfils.

Not only does Djokovic have the momentum from his winning streak, he will also have rest going into the match. The 24-year-old Serbian didn't face Fabio Fognini in the quarters due to the Italian's leg muscle injury.

Should Djokovic defeat Federer, he would match Ivan Lendl's 44-match winning streak dating back to the early 80s, and come within two wins of Guillermo Vilas's 46-match streak in 1977.

The Nadal-Murray match pins perhaps the best red clay player of all-time in Nadal, and the best tennis pro on the circuit to have never won a major in Murray.

Nadal is trying to repeat as champion, and after struggling against John Isner in a five-set match, has yet to concede a set since then. After losing to Djokovic in Madrid, Nadal would want nothing more than to bounce back with another French Open title victory.

Nadal won't be looking past Murray, but Nadal will certainly be disappointed should he lose in the Final.

Murray came from two-sets down to beat Viktor Troicki in the fourth round, and then followed that with a straight-set victory over Juan Ignacio Chela in the quarters.

The Scottish star has never come this far in the French, and has proven to be a solid clay-court player.

Perhaps in a year that has four top seeds in the tournament, the underdog Murray will be the one to surprise us all and beat both Nadal and either Djokovic or Federer.

No matter what happens on Friday and Sunday, the 2011 French Open has already proven to be a special one.

This weekend has the potential to go down as one of the very best in French Open history.