TENNIS-GBR-ATP-FINALS

Switzerland's Roger Federer remonstrates with the umpire after being made to replay a point his second set tie-break against Alexander Zverev during their men's singles semi-final match on day seven of the ATP World Tour Finals tennis tournament at the O2 Arena in London on November 17, 2018. - Alexander Zverev beat Roger Federer 7-5, 7-6 (7/5) on Saturday to reach the title decider at the ATP Finals in a match that ended in confusion after a ball boy's fumble forced a point to be replayed. Zverev won the replayed point with an ace and nudged into a 5-4 lead before Federer inexplicably netted with a simple forehand volley to hand the German two set points, the second of which he took on his own serve. (Photo by Ben STANSALL / AFP) (Photo credit should read BEN STANSALL/AFP via Getty Images)