Former world’s no.1 and four-time Grand Slam champion Jim Courier dropped a big bomb that could forever separate Roger Federer from his rival Rafael Nadal.

The US Tennis legend said he has a feeling Nadal’s career won’t last as long as Federer’s primarily because of the Spaniard’s physically-demanding playing style that demands a lot of energy and puts too much strain on his joints, particularly on his knee.

Courier, who two championships each at the Australian and French Open in the early 90s, thinks there’s a lot of to appreciate about Federer’s ballet-like playing style and worries about Nadal’s warrior-like approach.

While Nadal has been the more dominant player of the two over the past three years, there’s a doubt in Courier’s mind that the Nadal will be able to play at a high level in the coming years, as he believes the wear-and-tear of his bludgeoning style of play will eventually take its toll on his body.

On the other hand, the American had an opposite view with regard to Federer’s longevity in the sport, believing the Swiss Maestro will continue to play strong in the next 3 to 5 years due to his suave and somewhat artistic technique.

"The amount of energy that Roger uses to hit a shot is way less than what used by Nadal when hitting his strokes. Federer interprets tennis as if it was a dance, a ballet on the court. Nadal instead, when he is playing, it looks as if he is battling," Courier said of the difference between Nadal’s and Federer’s playing style via Tennis Tonic.

"That sort of explains why the Spaniard will not enjoy the same longevity as Roger, even though we would all love to see Rafael competing when he is 33. Credit must be given to those who taught Roger to play that way."

The 28-year old Nadal is just three Grand Slams away to tying Federer’s 17 Grand Slam haul. However, over the past three years, Nadal has experienced all sorts of injuries, from his bothersome left knee to a broken right wrist that left him out of the North American hard court season, including the US Open.

Meanwhile, Federer enjoyed an unexpected resurgence at 33-years old, racking up five ATP titles (including two ATP Masters 1000 championships), reaching the finals of the Wimbledon Open final for first time in two years and coming close to retaining the world’s no.1 ranking this year due to his consistency in every tournament he played.