American, Jack sock became the first of his kind to reach the last four of the ATP finals for 10 years, when he stunned world number three Alexander Zverev in a firecracker of a match yesterday, Nov 16.
The world number nine, who barged through the back door to qualify for the London showpiece by winning the Paris Masters.
Roger Federer won the Boris Becker group, having battled back to beat Marin Cillic earlier to post a perfect round-robin record at the event for the 10th time.
Results from the ATP World Tour Finals Men’s Singles Round Robin Group Boris Becker matches today, Nov 17.
Group Boris Becker
1. Roger Federer
2. Jack Sock
3. Alexander Zverev
4. Marin Cilic