Andy Murray's ability to overcome his demons and finally win a Grand Slam singles title resulted in a huge power shift for the ATP World Tour.

No longer do we have three men sitting on top, jockeying for the position as the world's No. 1 performer. Murray is here, and he doesn't seem prepared to go anywhere.

With that ascension comes a clashing of the best talent, and Murray cannot expect to open up 2013 with wins at the top events. One player in particular, Novak Djokovic, is ready to challenge the British star, and will make life difficult for him when a new slate of Grand Slam tournaments commences.

Murray-Djokovic appears to be a rivalry that could sustain itself for many years. Both players have come into their own the last few years, and continue to make improvements to their already immensely talented bag of skills.

In 2012 Murray has had Djokovic's number, ousting him in the London Olympics as well as beating him in the recently concluded, five-set marathon of a final match at the U.S. Open. Djokovic has gotten the best of Murray, though, as he beat his British counterpart in the final of the 2011 Australian Open.

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For many years the sport relied on the yearly battles between Roger Federer and Rafael Nadal. Both men dominated the biggest tournaments and found themselves competing against each other when it mattered most.

This isn't to suggest those two men are done being fixtures in Grand Slam tournaments. But when younger, talented superstars come along and prove they have that winning gene, it's hard not to take notice.

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As the 2012 season comes to a close, it's interesting to look back and realize each of the top four players claimed a Grand Slam title. But that parity may not hold for long, as we may have found a new duo of stars who could very likely dominate the tennis landscape.

Tennis still has too many good competitors for two men to monopolize the top two spots in the world rankings, but as we have seen in 2012, Murray and Djokovic mean business, and could battle for tennis supremacy as soon as next year.