Roger Federer and Rafael Nadal have surprised me for one reason says Jo-Wilfried Tsonga

Roger Federer and Rafael Nadal's renaissance in 2017 may have been one of the sporting narratives of the year, but according to rival Jo-Wilfried Tsonga the pair's return to the summit of men's tennis is no surprise.

Despite both starting the year outside of the world's top eight, Federer and Nadal have dominated the season, winning two grand slam titles each and claiming five of the eight completed Masters Series 1000 events to surge into the top two in the ATP rankings.

After a long-running battle at the top of the standings, Nadal confirmed himself as the year-end number one with a second-round win at the Paris Masters to become the oldest man to finish the year atop of the rankings since their introduction in 1973.

"I think it's a big achievement," said Tsonga. "I know what it means to be at my level. So I can imagine to be even better. It's a lot of sacrifice. It's a lot of work. It's also a lot of pleasure for sure. But, yeah, you give a lot of yourself and so, yeah, I know what it means and to do that is big."

Tsonga has spent much of his career in the shadow of Federer and Nadal, but has not been shocked by their comeback from respective knee and wrist injuries. Even so, the Frenchman could never have predicted their trophy-laden careers that sees them currently as the two most successful players in grand slam history, with 34 titles between them.

"I'm not surprised about the year they had; I'm surprised about the career they had," he added. "We all have in mind that Roger won 19 Grand Slams and Rafa won Roland Garros 10 times almost in a row, which is just unbelievable. And so, yeah, what can we say about it except [it is] magnificent."

Federer and Nadal's success has come against the backdrop of season-ending injuries to the likes of Andy Murray, who began the year as world number one, Novak Djokovic and Stanislas Wawrinka.

The likes of young pretenders Alexander Zverev – who won his maiden Masters Series 1000 events in Rome and Montreal – Dominic Thiem and Lucas Pouille have also enjoyed decent seasons, but none have been able to break Federer and Nadal's stranglehold on the sport.