Novak Djokovic and Andy Murray have played in the last two Grand Slam finals, and it's easy to imagine their rivalry overshadowing an aging Roger Federer and an injury-plagued Rafael Nadal in the years to come.But the second-ranked Federer will have none of it.As he prepares to defend his Dubai Championships title, the 31-year-old Federer said Sunday he is playing "excellent tennis" and is confident he can overtake Djokovic for the top spot.He acknowledged, though, it will be a challenge given that he plans to scale back his schedule in 2013. He wants to take several weeks off before the start of the clay season."Absolutely realistic, if you play great," Federer said of returning to No. 1, a spot he last held for 17 weeks until Oct. 29, breaking a record of 286 weeks at the top held by Pete Sampras."Time will tell," Federer said. "I know it's possible. I know it's possible to win tournaments. But right now, a big focus is on making sure every tournament I enter that I'm perfectly prepared, like for here, for Australia, for Indian Wells."Federer also brushed aside talk of retirement, making it clear he remains healthy and hungry to win more trophies, including another Grand Slam title - preferably Wimbledon, which he has won seven times. He is going for his sixth title in Dubai.The 17-time Grand Slam champion added to his total with a Wimbledon title in 2012 but lost in the quarterfinals of the U.S. Open and the semifinals of this year's Australian Open."I want to give myself the best possible chance to play as long as I can," Federer said."Eventually, it will be clear that it is time to stop, but the time is definitely not now," he said. "But then again, things change very quickly. You have to be ready for it and open to it. I'm not naive that I can play for 15 more years, but I would like to give myself a chance to play for many more years to come. I'm happy with where my body is at."Federer said the recent focus on a Djokovic-Murray rivalry made sense to some degree. But with four different players winning the four Grand Slam events last year, he said it was premature to turn the men's game into a two-man competition."Yes, they have played more often than not, and they have played in some big matches and very often the matches have been very good. So naturally that is what the media looks at. I understand that," he said. "It's all a question of how you see things. Rafa also has not been involved in this whole process the past seven months, so you don't want to jump the gun too quick."Djokovic, who is also in Dubai and going for his fourth title, agreed."I cannot pick (Murray) over Roger and Rafa because all three of them are still my biggest rivals," Djokovic said. "I cannot pick one of those three guys because Roger and Rafa have been so dominant in our sport and they have still - from all of the active players - the biggest rivalry."Djokovic said he was impressed with what he saw from Nadal in Brazil, where the Spaniard won his first title earlier this month since returning from a knee injury."He's still playing really, really good on clay, and I didn't expect any different," Djokovic said. "Again, I'm not in his shoes and I don't know how he physically feels. ... I'm sure that's going to give him a lot of confidence for the rest of the season, because that's what he wanted. It doesn't matter at what level and it's great for tennis that he's back - there's no question about it."After Djokovic won the Australian Open, attention turned to whether he can match his 2011 exploits, when he captured three major titles, had a 43-match winning streak and finished the year 70-6. The Serb said he was "in a strong position" to win more Grand Slam championships in 2013 and that he was "not hiding" the fact he wanted to win the French Open - where his chances have improved because of the injury troubles of seven-time champion Nadal.And in a warning to his rivals, he said he is in a better state of mind than he was a year ago."Mentally, I do feel a little bit more relieved than I was at the start of 2012," Djokovic said. "Following up after 2011 was an extreme challenge for me - mentally mostly - because I still played really well, but I found myself for the first time in a position to be the No. 1 in the world and to defend Grand Slam titles - three in a whole year."Right now, I've recuperated. I've learned my lesson; I've understood the experience that I went through, and I'm ready for new challenges."