Former French Open champion Albert Costa has revealed that he believes Roger Federer and Rafael Nadal could end the year as the top two players on the planet once again.

Costa was speaking in a recent interview about the staggering return to form of two of the sport's greatest competitors.

"Roger Federer and Rafael Nadal are probably going to end the season first and second in the ATP rankings," he said.

"The difference with the rest of the players is very big after five months of the season."

The Spaniard also spoke about Federer's decision to pull out of the French Open, understanding the Swiss maestro's decision.

"I think he is focusing on fast courts, where points are shorter and physical condition is not as important. Like Rafael Nadal, he has evolved his game style as well and he is hitting the ball harder.

"He has almost won everything he has played this season so far, so his methodology is working more than well.

"Again, it is sad that we cannot watch Roger Federer playing Roland Garros but in terms of extending his career, I think it is a good decision."

Federer withdrew from the Paris major in order to preserve his body and focus on the grass court season, a surface where he feels most at home on.

The 35-year-old Swiss has soared up the rankings after a stellar year that has seen him claim titles at Miami and Indian Wells, as well as his stunning victory at the Australian Open in January.

Having been in 17th, Federer sits pretty in fifth now. However, his current absence has seen Nadal overtake him the rankings.

Nadal, the undisputed King of Clay, is yet to drop a set on his way to the semi-finals at Roland Garros and is the favourite to get his hands on the famous Paris title for an unbelievable 10th time.

Wherever the two greats finish the year, it simply cannot be argued that the tennis world is a better place for having Federer and Nadal back at their absolute best.