• Novak Djokovic and Roger Federer

Novak Djokovic and Roger Federer (Photo : Wimbledon.com)

Former world's no.1 and 14-time Grand Slam winner Pete Sampras believes the title of the best tennis player ever will boil down between Switzerland's Roger Federer and Serbia's Novak Djokovic.

Sampras, who once held the honorary title during his prime, foresees a neck-and-neck race between Federer and Djokovic, although he had to admit that the latter has all the momentum to re-write history.

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"To beat Roger twice at the U.S. Open and Wimbledon, to beat Rafa at the French," Sampras said in an interview with CNN via Tennis.com.  "...Truly he's one of the greats of all time. He's won 11 majors, he's only 28. If he keeps this up over the next three, four years, he could very well pass me and get to 16, 17."

Sampras also said he was amazed by the way the 34-year old Federer performed this late in his career, adding that the Swiss 'is almost better' than he was racking up Grand Slams and breaking all sorts of records several years ago.

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On the other hand, the American tennis legend warned not to count out Rafael Nadal from the equation. Despite his struggles the past few months, Sampras is very aware of the Spaniard's ability to bounce back and dominate again in the tour.

Sampras didn't see any major problem in Nadal's game. As a matter of fact, he thinks Rafa only needs to regain the killer instinct and aggressiveness to be back in his old, dominant form.  

"He's hitting a lot of short balls," he said. "He's not as aggressive. He just seems really tense out there, he's nervous. When he's losing on clay that's shocking to me ... But it's not over for him. He's too good. He's won too much."

The 28-year old Djokovic has won 11 of the last 21 Grand Slams and have been on top of the world rankings for most of the past five years.

Federer, meanwhile, reached the finals of Wimbledon and US Open, and continues to be a major contender in every tournament. He suffered a bit of a setback as of late after suffering a knee injury (torn meniscus) in January, but pictures of his training suggests Federer is ready to go for the remainder of the season.