The 2015 ATP season has now been reduced to its last handful of matches with the ATP World Tour Finals set to wrap up this weekend.  With the field consisting of the year's top eight performers, there has been plenty of scintillating tennis on offer throughout the week, and it looks promising that the trend will continue through this weekend.  A particularly intriguing semifinal showdown has come to fruition, with Novak Djokovic set to take on Rafael Nadal in a match that could help determine if 2015 ends with the status quo intact or signals signs of change for 2016.

As members of the Big Four, Djokovic and Nadal are used to the spotlight, but they arguably grabbed more headlines this year than virtually any other player.  In the case of Djokovic, those headlines were almost all positive.  He spent the bulk of 2015 on fire, scooping up the year's first four Masters 1000 titles and six in total.  He was also stingy at the majors.  Djokovic won three of four and fell just one match shy of sweeping all four thanks to his loss to Stanislas Wawrinka in the final of Roland Garros.  It has been the best season of his career and one of the most dominant seasons in tennis history.

Whereas Djokovic was able to bask in his success, Nadal was left to languish in turmoil.  The Spaniard, who has so often been able to defy the odds when coming back from an injury hiatus, was never quite able to tap into his best over the course of this year.  He freely admitted to a confidence crisis as he suffered shocking losses and failed to win a title during the spring clay-court season.  The low point came when Nadal lost to Fabio Fognini at the US Open, marking the first time in his career that he had lost a match at a major when winning the first two sets.   All told, it has made 2015 his worst season in a decade.

Things, ironically enough, began to turn around for Nadal this autumn, however.  While he has not been as dominant as Djokovic, who won titles in Beijing, Shanghai, and Paris, the Spaniard has started to string together some successes.  He reached the finals of both Beijing and Basel, the semifinals in Shanghai, and the quarterfinals in Paris.  Those runs gave him the boost of confidence he needed before arriving in London, and it has been evident in his level of play.  Nadal has been the man to beat within his group, where he has finished first.  Djokovic, by contrast, has looked sub-par in the last couple of matches in his group, during which he lost to Roger Federer and experienced some hiccups during his victory over Tomas Berdych.  The respective roads that both men have taken to set up this blockbuster semifinal are what add to the intrigue and could have potential ramifications going forward.

Djokovic is looking to cap off his tremendous season with a record-breaking fourth consecutive ATP World Tour Finals title.  He has been a tough riddle for virtually every player to solve this year, and he would love nothing more than to end 2015 on a high note and ensure that the rest of the field has every reason to believe his reign over the sport will continue in 2016.  Of course, Nadal would love to be the player to spoil the party.  The Spaniard has struggled with his form and belief all season, but a victory over Djokovic and possibly a first title at the prestigious year-end championships would go a long way towards repairing his damaged psyche and aura.  To be able to pull off such an impressive feat on his least favorite surface would also send a strong message to his opposition that they can expect a much different and more dangerous Nadal next year.

For sure, there will be plenty riding on the line in Saturday's semifinal match between Djokovic and Nadal.  By virtue of the event itself, that was always going to be a given.  But there is an added layer of importance there as well.  A single encounter does not make or break players as accomplished as Djokovic or Nadal, but this semifinal has all of the makings of a match that could prove pivotal heading into 2016.