Greece's Stefanos Tsitsipas booked a spot in the championship match of the elite, season-ending ATP Finals for the first time with a 6-3, 6-4 victory here Saturday over six-time champion Roger Federer.

The 21-year-old Tsitsipas had defeated the 38-year-old world No. 3 in four close sets early this year at the Australian Open and he looked at London's O2 Arena like a player who knows he belongs on court with the veteran Swiss great.