Former world no.6 reveals the most impressive aspect of Federer's resurgence to world no.1

Roger Federer is playing better now than during his younger days – not the first time that has been said since his return from injury at the beginning of 2017. Chanda Rubin, a seven time singles WTA Tour winner is the latest to label the Swiss maestro "unbelievable".

The Swiss ace has surprised everyone following his return — after six months out with an injury — at the start of last season and continues to do so with his appetite to add more titles to his already overflowing CV. Federer has won nine titles in the last 13 months, which include three Grand Slams, taking his overall major tally to 20 men's singles titles.

When the 36-year-old won the Australian Open title last year, it was put as a one off owing to injuries to Andy Murray and Novak Djokovic, but he proved that he is back to his very best by winning further titles and ending the year as the world number two behind another veteran and long-time rival Rafael Nadal.

Federer has continued his form into 2018 and is currently unbeaten this year having defended his crown in Melbourne and then added the Rotterdam Open title to become the oldest world number one in men's tennis.

The 20-time men's singles Grand Slam champion has no plans of hanging up his racket and has shown that he still has the passion to play and win titles. According to Rubin, it is that appetite which he still possesses after two decades on the professional tour that is impressive.

"How he kept getting better, that to me is what is most impressive," Rubin said, as quoted by the Express. "He still wants more and he still has that motivation."

"It has been pretty amazing. Considering the year he had last year I actually thought he had gotten back to number one.

"Just because he played so well and won Grand Slams again. He is continuing to cement his legacy and it has been unbelievable to watch," the American former world number six added.