Alexander Zverev (in pic) 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 and high drama.

The German, leading the charge of the new generation against the old guard, is now just one win away from the biggest title of his career but the Swiss must wait for a tilt at his 100th tournament victory. The end of the match was overshadowed by an unusual incident, Zverev stopping a rally with Federer leading 4-3 in the second-set tie-break after a ballboy dropped a ball, forcing the point to be replayed.