Watch: The GOAT or a goat? Little kid floors Roger Federer with adorable question ahead of US Open

Not many serves have managed to catch Roger Federer on the wrong foot during the course of his long, glittering career and the Swiss maestro is known for handling his media interactions with equal grace. But the 36-year-old perhaps found his match in an adorable question served up by a little kid ahead and it concerned him being 'The GOAT' or 'a goat'.

Just in case you're wondering, Roger Federer is often called The GOAT - Greatest of all time- in tennis. At a question-answer session before the US Open, a young fan, Zizou Ahmed, asked Federer the reason behind the tag, but he wasn't quite aware that there was an acronym involved. Little Zizou also managed to strongarm Federer into pinky promising to play him once he turns pro.

Despite being taken by surprise initially, Federer addressed the question in trademark 'Federer'esque elegance.

Here's a video of the entire exchange and the transcript for your convenience.

#NetGenerationKidcaster @AceZizou met @rogerfederer. So why do they call him the 🐐?

https://t.co/EJamIca7jr #USOpen pic.twitter.com/ipD7RaFRrQ

— US Open Tennis (@usopen) August 26, 2017

Zizou: I wanted to ask you, Switzerland is really cold right, there isn't too much livestock., So why do they call you the goat?

Federer: Sometimes...sometimes they call me that. I don't call myself that. We don't have a lot of animals obviously. I am also a part of the livestock there, so"

Zizou: You have been the most consistent player of all time. Umm...can you continue to play for 8-9 years so that I can play you when I turn pro.

Federer: If you can make it on tour, I will make sure that I come back for you.

Zizou: Is that a promise?

Federer: Almost...almost...pinkie promise.

Federer will be gunning for his 20th Grand Slam at the US Open and the Swiss has been in terrific form this year, having bagged the Australian Open and the Wimbledon already. The 36-year-old hadn't won a major since the 2012 Wimbledon before his incredible revival this season.

The 5-time US Open champion will kickstart his campaign against US player Frances Tiafoe on Tuesday.

Read more:

Wimbledon: Roger Federer beats Marin Cilic in final to clinch record 8th title

Maria Sharapova shocks Simona Halep on her emotional US Open return