Roger Federer and Andy Murray.
Murray and Federer are half of the "big four" in men's tennis, and the stamp that Murray left on the 2012 year concurrently gives Federer a new lease on life.
Djokovic and Federer share a 16-13 head-to-head record—advantage Federer, and despite the fact that Nole had that terrific run of 41 straight wins to kick off 2011, the two have only met in one Grand Slam final.
Djoker has been a tough roadblock for Federer on several other occasions, but it is not his rivalry that will rejuvenate Roger.
Nadal needs no introduction as a rival to Federer, as he firmly held that crown primarily between 2005 and 2009. That rivalry will continue as soon as the two meet again, but Rafa's absence from competitive play since sustaining that second-round loss at Wimbledon, has put said rivalry into serious question.
Sunday July 6, 2008 was the Wimbledon final between Nadal and Federer, and that distinct moment in tennis history unequivocally marks the height of their storied rivalry.
Fast-forward to 2013, their rivalry doesn't carry the appropriate weight to refresh Federer's career.
Not to devalue the Bjorn Borg vs. John McEnroe and Pete Sampras vs. Andre Agassi rivalries, but it's a fair to say that tennis' biggest rivalry ever might be the composition of Murray, Djokovic, Nadal and Federer, as they have each taken turns beating each other on the largest stages.
History may infer that Federer has more compelling rivalries with Nadal and Djokovic when each are at their best, but Murray now assumes the role of the rival who gets the best out of Federer.
It's Murray who has the closest career head-to-head against Federer at this point—a 10-9 slight edge for Andy.
There's a uniqueness to Murray's game, something that is sure to revitalize Federer's career looking ahead to 2013.
Strong signs of Federer's resurgence:
The 31-year-old Federer closed the book on Murray's Olympic Gold-medal and U.S. Open Championship season in the semi's of the ATP World Tour Finals—this after a grueling 12-month schedule.
The Swiss champion clearly used his semifinal match against Murray to send a message to tennis fans everywhere that the tour better not sleep on him in 2013.
Roger was subsequently ousted in the final by the third member of the big four and World No. 1 Novak Djokovic, but it was evident that Murray had gotten the A-game out of Federer—Djoker's perseverance won out.
Scotland and Switzerland mix well
Federer's sustained dominance into his 30s can best be attributed to Murray, in spite of the fact that Andy's the least celebrated and appreciated member of the big four.
Including the London Olympics, Federer and Murray met five times in 2012—three finals and two semifinals, with Federer winning two of those finals.
Murray may not have the return-game of Nadal or Djokovic, but his tireless effort to gain the clout of his three contemporaries seems to do something to Federer that Nole and Rafa can't produce.
When Roger and Andy face off, it's like Federer is transported back in time to that mythical-like phenomenon he was in his prime.
Is rival Andy Murray the best man to revitalize Federer's career?
Murray's mental demons will never go away completely, but his counter-punching ability coupled with Federer's offensive artistry go together better than peanut butter and jelly.
Nadal's impact upon his return is all speculation right now, and Djokovic can't have a carry-over from 2012 where he keeps playing from behind, because that'll catch up with him.
Murray will definitely be more of a focal point in 2013, and it will be the season of Murray and Federer.
Their rivalry will perpetuate Andy's success, but Roger will be the bigger beneficiary and will emerge to have at least one more dominant season in his Hall of Fame career.