Former world number five Henri Leconte has praised the career resurgences of Rafael Nadal and Roger Federer, attributing their success to changes in their games as well as injuries to key players.

Nadal has won six titles in the calendar year, including a 10th French Open title as well as his 3rd US Open title as the Spaniard currently sits atop the rankings as world number one.

Meanwhile, Federer also has six titles, winning the Australian Open by defeating Nadal in a five-set thriller in what was his first Grand Slam victory since 2012.

He then went on to win an additional five titles, including a record-breaking 8th Wimbledon crown as he currently sits at number two in the ATP tennis rankings.

The duo's form has turned the clock back to the old days where they were both dominating tennis before the rise of the rest of the Big Four in Novak Djokovic and Andy Murray.

Leconte is not surprised that the long-time rivals are back on top, stating that the only surprise is the number of players suffering from injuries this year such as Djokovic, Murray, Stan Wawrinka and Kei Nishikori, all of whom will return at the 2018 Australian Open.

"Roger and Rafa have dominated like the old days," Leconte said, as quoted on Sky Sports. "It seems like they have only two players on the ATP tour but it's been a vintage year because of the amount of injuries."

Regardless of the injuries to many key players, both Nadal and Federer have considerably stepped their game up. With the pair both taking time off in 2016, Leconte adds that the Spaniard is now more confident and aggressive while the Swiss ace is replenished mentally and physically.

"Tennis has changed. It's quicker, harder, and players have to be more prepared to stay at the very top level," Leconte explained.

"Roger took time off completely which helped him recycle his mental energy and physicality. He was very happy to come back at Wimbledon and play a different type of tennis.

"Rafa was the opposite in the fact that he has become more and more confident, raising his game to become even more aggressive - it's a big change."