The Australian Open is missing Rafael Nadal. 

We have known since Dec. 28 (ESPN) that he would not be competing in the Australian Open, but the further we advance in the tournament, the more his presence is missed.

As the final four is assembled in the men's draw, the void is clear.

Rafa is still one of the four best players in the world; having a Grand Slam event without him just seems unofficial to a degree.

While whoever emerges victorious in Melbourne will have earned the trophy they hoist, there is no doubt the victory would carry more luster if the field were complete with all of the sport's biggest stars.

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That will especially be the case if Roger Federer wins his fifth Aussie Open title.

Nadal has long been Fed's nemesis, holding a 20-10 advantage over him in their careers. There will be talk—from pro-Nadal fans, mostly—that Federer has again captured the crown in a Nadal-less field.

Federer won Wimbledon in 2012 after Nadal was upset in the second round by Lukas Rosol. The Swiss legend's victory was sweet, but it would have been sweeter had he gone through Rafa.

Barring an upset victory from Jeremy Chardy over Andy Murray or Jo-Wilfried Tsonga over Federer, the semifinals will include Murray, Federer, Novak Djokovic and David Ferrer.

All four are obviously world-class players, but Ferrer is the name that is most out of place. He earned his spot in the semifinals with a hard-fought (4-6, 4-6, 7-5, 7-6, 6-2) comeback win over Nicolas Almagro in the quarterfinals.

However, it is hard not to think that Nadal would be occupying his spot in the brackets, if he were healthy. The seedings would have been a little different as Ferrer wouldn't have been a fourth seed in a field that included Nadal.

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Ferrer is 5-17 against his countryman in his career, so the latter's absence is significant.

In addition to missing Nadal for his elite standing in the sport, the Australian Open is also lacking the unbridled passion the Spanish star brings to his matches.

When he's right, his body language and style are among the most charismatic and polarizing in the sport. He makes you love him or hate him; but if you like the sport, you'll almost certainly be watching him.

The tournament has had its share of spirited matches, but it is missing that spark that Rafa genuinely provides.