• Novak Djokovic. Rafael Nadal and Roger Federer

Novak Djokovic. Rafael Nadal and Roger Federer (Photo : Getty Images)

Roger Federer admitted rivalry with Rafael Nadal has been the greatest in his career, while insisting that Novak Djokovic is still beatable despite the Serb's tennis dominance.

Federer spoke about his rivalry with Nadal and Djokovic as chronicled by The Guardian's Simone Hattenstone in a piece that documented the highlights of the Swiss Maestro's illustrious tennis career.

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The 17-time Grand Slam winner confessed his greatest rival in the sport has been Nadal because of their epic matchup at Wimbledon back in 2008, when a 26-year-old Federer got defeated by the Spaniard in classic five-setter final round.

"For me, he [Nadal] has been [the greatest rival]. It could still change if I play Novak another few times in bigger matches. Novak and I have obviously had really big matches, but somehow the match-up with Rafa will always stay unique - because of the Wimbledon final in 2008," Federer said.

Federer has only won 11 of all his 34 career head-to-head matches with Nadal and has only defeated the Spaniard in two of their last seven outings. Their most recent match was last year at the ATP Swiss Indoors in Basel, with Federer defeating Nadal in the final round.

Federer also talked about his other rival, Djokovic, who has been dominating the tennis scene in the past two seasons. Djokovic has won four of the last five Grand Slam events and is in pole position for a calendar sweep and a Golden Slam this year. But despite the Serb's relentless effort to stay at the top of the rankings, Federer believes he can still beat Djokovic.

"Is Djokovic now the man to beat? Absolutely. Does he deserve to be where he is? 100 per cent. But is he beatable? Yes, of course he is. I beat him last year three times," Federer said.

While, Federer has shown he is capable of taking down Djokovic, the 34-year-old Swiss has not beaten the Serb in their last four Grand Slam event match. Federer's last victory over Nole was in the round robin stage of the Barclays ATP World Tour Finals last year, but it has becoming a trend for Djokovic to defeat Federer in important matches and major events.

Federer has yet to win a title this season, no thanks to injuries that forced him to miss tournaments, most recently the French Open last month. These setbacks also kept Federer without a title this season, although the Swiss feels he is finally close to becoming lethal again as he approaches Wimbledon, which starts on June 26.

Despite losing against Germany's Alexander Zverev in the semifinal round of the Gerry Weber Open in Halle, marking the first time Federer failed to compete in the final in his last 11 appearances, the world No. 3 still takes pride of his run at the tournament. For Federer, a semifinal loss means more than a mark in the losing column, taking it as a progress to his quest of returning back to his old form.

"It's been intense and it's been busy and it's exactly what I needed. At least I have a clear picture now where my game is at, what I need to do and without Stuttgart and Halle I wouldn't have that. I have more clarity now," Federer said, reports the ATP's official website.

"But I'm okay and I'm pleased on how I played, how I'm feeling and now we've got enough time before Wimbledon to get ready for that."

Federer will attempt for a record eighth title at Wimbledon, where he will have a chance to meet Djokovic and test his claims of being able to beat the 12-time Grand Slam winner.