The greatest current rivalry in tennis continued last night, when Roger Federer and Rafael Nadal met in the semifinals of the Australian Open.

This meeting was slightly different – especially since the last time Federer and Nadal met in the semifinals of a major was 2005. Given the fact that they were number one and number two in the world for so long, they were usually on different sides of the draw.

Things are different now, though.

Nadal is still number two but Serbia’s Novak Djokovic claimed the number one spot for the first time last year after winning three of the four Grand Slams. Nadal won the fourth.

Now, it can be argued that at 30 years old, Federer is starting to slow down. Given the ease at which he raced through the draw at this year’s Open, however, that doesn’t actually appear to be true.

It can also be argued that, given the physical nature of his play, Nadal’s body is starting to break down. Despite the fact that he said he was taking time off after the Australian Open to rehab his shoulder (and his right knee has been heavily strapped throughout the tournament) Nadal has showed no signs of slowing down, though.

Both these guys proved Wednesday night (Thursday night in Australia) that they are both hungry to reclaim their former glory.

It was Nadal, though, who came out on top 6-7(5), 6-2, 7-6 (5), 6-4 in a little under four hours of play -- improving his record to 8-2 over Federer in majors. So how did he win? Actually, the same way he always does – he just wore Federer down. Plain and simple, he out grinded him, out shot him and ultimately out thought him.

Nadal came out a bit slow in the first set and Federer – who now is 0-9 in his last Grand Slam appearances -- was on fire. He broke Nadal’s serve early and looked to be on the way to coasting through the first set.

Always tenacious, though, Nadal clawed his way back and evened things up late in the first set. He would ultimately drop the first set in a tiebreaker, but it was clear that momentum was starting to swing his way.

Then, in the second set, Federer had another early break. This time, when Nadal broke back to even the game count at two, he was the one who cruised through the second set – making Federer look more like a qualifier than the winningest man in tennis history.

In the third set, Federer and Nadal traded breaks until they reached another tiebreaker. This time, Nadal jumped out to what seemed like an insurmountable lead – 6-1. The fact that he only won the tiebreaker 7- 5 is more of a commentary on Federer’s desperation than Nadal’s tennis playing. It was almost like Federer realized he couldn’t come back from being down two sets to one.

He was right.

In the fourth set, Nadal seemed to almost be toying with Federer. He threatened the Swiss wonder on almost every single one of his service games, before finally breaking in the ninth game of the set. He then fought his own nerves (and two break points) to ultimately win the match.

The question now becomes, can Nadal reclaim the number one spot when he meets either Djokovic or Britain’s Andy Murray in the final on Sunday? Mathematically, he can’t do it even if he does win the championship. Emotionally, though, I think Nadal would get more from a Djokovic win (especially since Djokovic beat him in two Slam finals last year).

After his rehabilitation break, Nadal will then enter the North American hard-court season a heavy favorite before returning to his beloved clay. That is, of course, if the 25-year-old Spaniard’s body holds up.

It’s no secret that Nadal has struggled with knee, shoulder and stomach injuries over the last few years. In fact, injuries have hampered his last two Australian Open appearances, helping him lose to compatriot David Ferrer and Murray the last two years.

A healthy Nadal is practically unstoppable – and I think Djokovic knows this. Despite his dominant year last year, I don’t think Djokovic actually played as well as most pundits thought he did. I think it was more that the rest of the men’s field also had a down year.

Now, I like Dojokovic, don’t get me wrong. I like his jovial nature and how passionate he gets on the court. I have nothing against him. I mean, I openly hate Murray, for example, but that’s not the case with Djokovic. Against anyone but Nadal, I root for him.

Ultimately, the thing is, I think this could be Nadal’s year to reclaim the number one spot. If he manages to win even two Grand Slams, that would bring his number to 12 – only four behind Federer (who is almost five years older). He could still have a good shot of taking Federer’s overall title.

For his part, I think Federer probably has one more Grand Slam title in him. But, if he’s going to win it, I think it’s going to have to be this year. I don’t think he can do it next year at the age of 31.

The big test for Nadal will come in Sunday’s final. I think it would be easier for him to beat Murray (who is known for choking in finals) than Djokovic. I know I always appreciate it when Murray loses (he really is a poor sport and a whiner). However, I think Nadal will get a bigger boost if he beats Djokovic.

Of course, if he loses to Djokovic, that creates a whole other problem doesn’t it?

What do you think? Will Nadal reclaim the number one spot this year or will Djokovic continue his winning ways?