Watch: Roger Federer calls his own service 'out' after hitting an ace

Roger Federer, heralded all across the globe for his flair and grace, gave an exemplary display of his trademark sportsmanship at the ongoing Rotterdam Open. During his quarter-final fixture against Dutch international Robin Haase, the Swiss master called his own serve out.

Leading the third set 1-0, 40-15 on the Central Court in Rotterdam, the 36-year-old served wide to Haase's forehand, appearing to ace his opponent. As the crowd cheered in appreciation, Federer calmly lined back to prep himself for the second serve.

A bewildered Haase soon called out across the court: "Roger, no one called 'out'."

The Swiss legend simply replied "It's out", prompting the chair umpire to declare the service as a ‘fault’.

In the end, it was too easy for the Federer as he won the point anyway on his second service. He took advantage of Haase's forehand error, eventually taking a 2-0 lead and bringing himself just four games away from earning a semi-final berth.

When the soon-to-be World No.1 says his serve is out......it's out 😂#abnamrowtt @rogerfederer pic.twitter.com/B4z4Cjx7HG

— Tennis TV (@TennisTV) February 17, 2018

With the win, Federer reclaimed the numero uno spot in ATP rankings after a little more than five years since he last held it, precisely 2050 days. Federer displaced Rafael Nadal from the summit after beating Robin Haase 4-6, 6-1, 6-1 in the last eight of the Rotterdam Open.

In the process, the ‘Swiss maestro’ also became the oldest World No. 1 in tennis history at the age of 36, surpassing Andre Agassi. The American held the previous record for the oldest world No 1 in Men’s tennis aged 33 back in 2003.