London: Greek sophomore tennis star Stefanos reaches the semi-finals of the NATO ATP Finals Group Stage while maintaining a fine performance. It was Stefanos' second success in the ATP Finals group stage. The 21-year-old Greek tennis star defeated Germany's rival Khalili Alexander Zveiro 6-3 and 6-2 in the Street Seats in a London ATP Finals Group Stage Men's Singles match. This is Stefanos' second consecutive victory in the ATP Finals group stage. They earlier defeated Russian player Danil Medvedev in their first match.