(AP) - Alexander Zverev, Germany, def. John Esner, United States, 7-6 (7-5), 6-3.
The world number one, Novak Djokovic, was the top scorer in the Goga Kuerten group, having previously qualified to the last box. Goku will meet South African Kevin Anderson in the semi-final.
Zverev knew that winning any result on Eisner at the O2 Arena in the British capital would have led him to the semi-finals.
The 21-year-old saved a crucial point in the 12th half of the first set with an overwhelming shot, finishing a crucial course, narrowly defeating the giant American (2.08m).
Zverev, who rose to fourth in the world, has won three trophies this year, including the Masters in Madrid. However, the player, described by the experts as the new generation yellow ball champion, has yet to achieve any remarkable results in the Grand Slam (best result of Roland's quarterfinal) Garros in 2018).
Zverev became the youngest player to reach the semifinals of the final round of the tennis season, since Argentine Juan Martin del Potro in 2009.
The eventual final between Federer and the 100th-minute winner is still possible, with the two semi-finalists going through the re-run of the 2015 final when the Serbian outperforms two groups.
