Wawrinka backs Federer to become oldest No.1

French tennis star Stan Wawrinka has backed eighteen-time Grand Slam champion Roger Federer to become the oldest player in history to seal the world number one spot at the age of 35.

Swiss star Federer recently climbed up four places to the sixth spot in the latest ATP rankings after lifting his fifth Indian Wells Masters title.

The 35-year-old continued his impressive return from six-month injury lay-off as he defeated Wawrinka 6-4, 7-5 in an all-Swiss final that lasted for one hour and 20 minutes.

It was his second win of the year following his triumph in the Australian Open and first major title triumph in four and a half years.

Reflecting on the same, Wawrinka insisted that Federer is not only back in form but he is also playing in a noticeably manner which gives him great chance to make his way back to the pinnacle of the rankings.

"He's playing really well, what is different maybe is he is playing closer from the baseline, preferring, using less his slice, he is using more top spin, putting more pressure all the time, returning better that's the difference I seem," Sport24 quoted Wawrinka as saying.

"For sure he has a shot for number one, he has just won the first Masters final. For sure he has a big shot," he added.

America's Andre Agassi holds the record of the oldest player to hold the men's No. 1 ranking, at 33.

Wawrinka also insisted that it is not at all shocking to see Federer---who has 90 career titles in his account--- return to such great form before adding that he was particularly impressed by his movement.

"From him nothing is a surprise, but for sure to see him moving that well at that age it is something amazing. It is good for me to see that you can be at the top (at that age). It is amazing to see how he is playing after a six-month injury," he added.

Federer will now face a strong challenge from old rival Rafael Nadal, who is bidding for his first ever win in Miami after losing in four summit showdown at the Key Biscayne venue.