Friday 17 November 2017 07:22, UK
Roger Federer was analysing his third straight win in the Boris Becker group at the ATP Finals when he was surprised by Jack Sock at the Sky Pad.
Six-time champion Federer went through the round-robin stage undefeated for the 10th time as he returned to haunt Marin Cilic with a 6-7 (5-7) 6-4 6-1 win at the O2 Arena on Thursday.
The Swiss superstar has reached the last four in 14 out of 15 appearances in the year-end tournament and will face David Goffin or Dominic Thiem on Saturday for a place in the final.
But first he analysed his latest win with Sky Sports' Mark Petchey, and things were ticking along nicely when a surprise appearance from Jack Sock in his Kansas City Chiefs' bobble hat caught the world No 2 off guard.
Federer also discusses his eyes when he serves and proves that he has a photographic memory after one of the shots of 2017 in Basel.
The season-ending extravaganza ATP Finals ends another memorable year which will be covered via our website www.skysports.com/tennis with live blogs, reports, reaction and expert analysis as the season reaches its climax.
On the move? Head to our app for mobile devices and iPad, or follow our Twitter account @SkySportsTennis to join in the conversation. Who will win the World Tour Finals this year? Have your say...
